Neuroimmune Mechanisms

and Chronic Fatigue Syndrome:

Will Understanding Central Mechanisms Enhance

the Search for the Causes, Consequences, and 

Treatment of CFS?

June 12–13, 2003

A Report of the Scientific Workshop Co-Sponsored by the NIH Office of Research on Women’s Health 

and the Trans-NIH Working Group for Research on Chronic Fatigue Syndrome

iii Speakers

1 Introductory Comments

1 Welcome

Vivian W. Pinn, M.D.

3 Welcome

Eleanor Hanna, Ph.D.

5 Introduction

Leslie J. Crofford, M.D.

7 An Overview of Chronic Fatigue Syndrome

Dedra Buchwald, M.D.

11 Session One: The HPA Axis 

Chair: Leslie J. Crofford, M.D.

11 Health Consequences of a Dysregulated Stress Response

Esther M. Sternberg, M.D.

17 Stress and the Augmentation of Immune Function

Firdaus S. Dhabhar, Ph.D.

23 Evaluating Immune Function in CFS

Nancy Klimas, M.D.

27 Stress and Antidepressant Modulation of the Limbic HPA Axis

Juan F. López, M.D.

33 HPA Axis and Autonomic Nervous System Function in Fibromyalgia

Gail Kurr Adler, M.D., Ph.D. 

37 Session Two: The Autonomic Nervous System

Chair: David Goldstein, M.D., Ph.D.

41 CNS and ANS Responses to Exercise in Patients with CFS

Peter D. White, M.D.

45 Corticotropin-Releasing Hormone, Insomnia, and Depression

Gary S. Richardson, M.D.

49 Session Three: Cytokines, Sleep, and the CNS

Chair: Harvey Moldofsky, M.D. 

51 Genetics of Sleep Regulation

Linda A. Toth, D.V.M., Ph.D.

Contents

Contents i
57 Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State

Mark R. Opp, Ph.D.

63 Mechanisms Underlying the Central Effects of Cytokines

James Krueger, Ph.D.

69 Session Four: Will Understanding Central Mechanisms Enhance the Search for the 

Causes, Consequences, and Treatment of CFS?

Chair: Dedra Buchwald, M.D.

71 Brain Stress–Response Circuitry in the Regulation of Physical and Affective States

Jon-Kar Zubieta, M.D., Ph.D.

77 The Cognitive Neuroscience of Fibromyalgia

Denise Park, Ph.D.

81 Sex and Gender Issues in Multisystemic Illnesses

Margaret M. Heitkemper, Ph.D.

87 Family Studies in Fibromyalgia

Lesley M. Arnold, M.D.

91 Biomarker Discovery in Illnesses with No Lesions

Suzanne D. Vernon, Ph.D.

95 Session Five: Therapeutics

Chair: Dimitris A. Papanicolaou, M.D.

97 Innovative Treatments in CFS

Daniel Clauw, M.D.

103 Cognitive Behavioral Therapy

David A. Williams, Ph.D.

109 Challenges in the Development of Acute and/or Chronic Pain Therapies

Lee Simon, M.D.

115 Session Six: Optimal Directions for Research of the CNS in CFS

Co-Chairs: Leslie J. Crofford, M.D., and Dedra Buchwald, M.D.

117 Appendix

117 Trans-NIH Working Group for Research on Chronic Fatigue Syndrome

ii Contents
Speakers iii

Gail Kurr Adler, M.D., Ph.D.

Assistant Professor

Department of Medicine

Brigham and Women’s Hospital

221 Longwood Avenue

Boston, MA 02115

Phone: 617-732-5661

Fax: 617-732-5764

E-mail: gadler@partners.org

Lesley M. Arnold, M.D.

Associate Professor

University of Cincinnati

College of Medicine

231 Albert Sabin Way

Cincinnati, OH 45267-0559

Phone: 513-558-4622

Fax: 513-558-4280

E-mail: lesley.arnold@uc.edu

Dedra Buchwald, M.D.

Professor of Medicine

University of Washington

Harborview Medical Center

325 Ninth Avenue

Box 359780

Seattle, WA 98104

Phone: 206-341-4439

Fax: 206-731-8247

E-mail: dedra@u.washington.edu

Daniel Clauw, M.D.

Professor of Medicine

University of Michigan

24 Frank Lloyd Wright Drive

Box 385

Ann Arbor, MI 48106

Phone: 734-998-6961

Fax: 734-998-6900

E-mail: dclauw@med.umich.edu

Leslie J. Crofford, M.D.

Associate Professor of Internal Medicine

University of Michigan

Room 5520 MSRB-1

1150 West Medical Center Drive

Ann Arbor, MI 48109-0680

Phone: 734-936-3257

Fax: 734-763-2025

E-mail: crofford@umich.edu

Firdaus S. Dhabhar, Ph.D.

Associate Professor

Ohio State University

4179 Postle Hall

305 West Twelfth Avenue

Columbus, OH 43210

Phone: 614-688-8562

Fax: 614-247-6945

E-mail: dhabhar.1@osu.edu

David Goldstein, M.D., Ph.D.

Chief, Clinical Neurocardiology Section

National Institute of Neurological Disorders 

and Stroke

National Institutes of Health

10 Center Drive, MSC-1620

Building 10, Room 6N252

Bethesda, MD 20892-1620

Phone: 301-496-2103

Fax: 301-402-0180

E-mail: goldsteind@ninds.nih.gov

Eleanor Hanna, Ph.D.

Associate Director

Special Projects and Centers

Office of Research on Women’s Health

National Institutes of Health

6120 Executive Boulevard, Room 150A

Bethesda, MD 20892-7116

Phone: 301-435-1573

Fax: 301-402-0005

E-mail: hannae@od.nih.gov

Speakers
Margaret M. Heitkemper, RN, Ph.D.

Professor

University of Washington

1959 NE Pacific

Seattle, WA 98195

Phone: 206-543-1091

Fax: 206-543-4771

E-mail: heit@u.washington.edu

Nancy G. Klimas, M.D.

Professor of Medicine

University of Miami VA Medical Center

1201 NW 16th Street (111-I)

Miami, FL 33125

Phone: 305-575-3267

Fax: 305-575-3139

E-mail: nancy.klimas@med.va.gov

James Krueger, Ph.D.

Professor

Washington State University

College of Veterinary Medicine

264 Wagner

Pullman, WA 99164-6520

Phone: 509-335-8212

Fax: 509-335-4650

E-mail: Krueger@vetmed.wsu.edu

Juan F. López, M.D.

Associate Professor

Department of Psychiatry

Assistant Research Scientist

University of Michigan

Mental Health Research Institute

205 Zina Pitcher Place

Ann Arbor, MI 48109-0720

Phone: 734-615-3144

Fax: 734-647-4130

E-mail: jflopez@umich.edu

Harvey Moldofsky, M.D., FRCP(c)

Professor

Sleep Disorders Clinic

Centre for Sleep and Chronobiology

340 College Street

Suite 580

Toronto, Ontario M5T 3A9

Phone: 416-603-9531

Fax: 416-603-2388

E-mail: h.moldofsky@utoronto.ca

Mark R. Opp, Ph.D.

Associate Professor

Anesthesiology and Molecular and

Integrative Physiology

University of Michigan

1150 West Medical Center Drive

7433 MS Building 1

Ann Arbor, MI 48109-0615

Phone: 734-615-8768

Fax: 734-764-9332

E-mail: mopp@umich.edu

Dimitris A. Papanicolaou, M.D.

Assistant Professor of Medicine

Department of Medicine/Endocrinology

Emory University

Room 1307, West Wing WMRB

1639 Pierce Drive

Atlanta, GA 30322

Phone: 404-727-1395

Fax: 404-727-1300

E-mail: dpapani@emory.edu

Denise Park, Ph.D.

University of Illinois at Urbana–Champaign

Beckman Institute

405 North Mathews Avenue

Urbana, IL 61801

Phone: 217-244-6348

Fax: 217-244-9381

E-mail: denisep@uicu.edu

Vivian W. Pinn, M.D.

Director

Office of Research on Women’s Health

National Institutes of Health

9000 Rockville Pike

Building 1, Room 201

Bethesda, MD 20892

Phone: 301-402-1770

Fax: 301-402-1798

E-mail: pinnv@od.nih.gov

Gary S. Richardson, M.D.

Senior Research Scientist

Henry Ford Hospital

Clara Ford Pavilion–3

2799 West Grand Boulevard

Detroit, MI 48202

Phone: 313-916-5182

Fax: 313-916-5167

E-mail: gsr@attglobal.net

iv Speakers
Speakers v

Lee Simon, M.D.

Director

Division of Anti-Inflammatory, Analgesic,

and Ophthalmic Drug Products

Food and Drug Administration

Office of Drug Evaluation V

Center for Drug Evaluation and Research

9201 Corporate Boulevard, N-314, HFD-550

Rockville, MD 20850

Phone: 301-827-2017

Fax: 301-827-2531

E-mail: simonl@cder.fda.gov

Esther M. Sternberg, M.D.

Director, Integrative Neural Immune Program 

Chief, Section on Neuroendocrine Immunology 

& Behavior

National Institute of Mental Health

National Institutes of Health

36 Convent Drive

Room 1A 23, MSC-4020

Bethesda, MD 20892-4020

Phone: 301-496-9255

Fax: 301-496-6095

E-mail: ems@codon.nih.gov

Linda A. Toth, D.V.M., Ph.D.

Professor of Pharmacology

Southern Illinois University 

School of Medicine

801 North Rutledge Street

Box 19611

Springfield, IL 62794-9611

Phone: 217-545-3053

Fax: 217-545-6263

E-mail: ltoth@siumed.edu

Suzanne D. Vernon, Ph.D.

Research Microbiologist

Centers for Disease Control and Prevention

1600 Clifton Road, MSA 15

Atlanta, GA 30333

Phone: 719-539-7828

Fax: 719-539-2058

E-mail: svernon@cdc.gov

Peter D. White, M.D., FRCP, FRCPsych

Barts and The London Queen Mary 

School of Medicine and Dentistry

University of London

Department of Psychological Medicine

St. Bartholomew’s Hospital

London EC1A 7BE

United Kingdom

Phone: 44 (0) 207 601 8108

Fax: 44 (0) 207 601 7969

E-mail: P.D.White@qmul.ac.uk

David A. Williams, Ph.D.

Associate Professor of Medicine

University of Michigan

24 Frank Lloyd Wright Drive

Box 385

Ann Arbor, MI 48106

Phone: 734-998-6865

Fax: 734-998-6900

E-mail: daveawms@umich.edu

Jon-Kar Zubieta, M.D., Ph.D.

Associate Professor

University of Michigan

MHRI 

205 Zina Pitcher Place

Ann Arbor, MI 48109-0720

Phone: 734-763-6843

Fax: 734-647-4130

E-mail: zubieta@umich.edu

I

am delighted to see so many individuals here with

an interest in chronic fatigue syndrome (CFS) and

this conference. I want to thank our co-chairs as

well as the participants and observers.

For some time we have recognized that CFS, because

it primarily affects women, is a disease that we could

acknowledge and claim as a condition on which the

Office of Research on Women’s Health (ORWH)

should focus. In 2001, the ORWH assumed the

responsibility at the National Institutes of Health

(NIH) for coordinating trans-NIH efforts related 

to CFS research. In addition, we brought on board

Dr. Eleanor Hanna, who had been working with 

the Trans-NIH Working Group for Research on 

CFS, to become part of our office and to take the 

lead for this specific area.

The CFS Working Group represents an important 

part of our mission to encourage and stimulate interdisciplinary research. CFS is one of the scientific areas

in which interdisciplinary collaboration will be vital 

to unlocking the essence of the condition. The CFS

Working Group’s initial effort in 2001 concentrated 

on preparing a program announcement to stimulate

and broaden the scope of CFS research. That announcement was published in December 2002 and was based

on recommendations from an ORWH-co-sponsored

state-of-the-science conference held in October 2000. 

In fiscal year 2002, the CFS Working Group focused 

its efforts on disseminating the program announcement and evaluating its effectiveness in developing a

research plan and a specific request for applications 

to supplement that program announcement.

We want this workshop to help explore ways in

which the neuroendocrine system acts as an intermediary between the brain and other body systems 

in explaining the diverse CFS symptoms. One goal 

is to determine whether or not these effects are 

primary or secondary in terms of central control 

in the brain. The chairs of today’s sessions and 

Dr. Hanna will provide additional guidance about 

the goals of the conference and the specific scientific

concepts to be addressed.

We look forward to the recommendations that you

will bring forward. The Trans-NIH Working Group

for Research on CFS and the Office of Research 

on Women’s Health hope to develop and support 

an interdisciplinary request for applications, based 

on the underlying biologic mechanisms and questions

identified at this scientific workshop. Your discussions

and your contributions will be extremely important

and will hopefully help us take the science to a different level—to help provide some of the answers for

which those who suffer from CFS yearn.

Introductory Comments 1

Introductory Comments

Welcome

Vivian W. Pinn, M.D.

Associate Director for Research on Women’s Health, National Institutes of Health

We want this workshop to help explore ways in which the

neuroendocrine system acts as an intermediary between

the brain and other body systems in explaining the diverse

CFS symptoms.

Introductory Comments 3

Welcome

Eleanor Hanna, Ph.D.

Office of Research on Women’s Health

We are so fortunate that CFS is under Dr. Pinn’s auspices. Not only has Dr. Pinn been a 

champion of women’s health, but also she has made sure that underserved populations 

and under-recognized diseases are not forgotten at the National Institutes of Health.

I hope that today is the first of many meetings in which we gather an interdisciplinary group together, 

while we wait for answers to come from genomics and proteomics, and that we can begin to help people 

who have chronic fatigue syndrome and other unexplained medical illnesses. I thank you all in advance 

for your hard work during the next 2 days. I also hope you have fun!

Welcome to all of the speakers and the 

meeting chairs, the NIH Coordinating

Committee, Dr. Pinn, and all of you in 

the audience. This is a working meeting, so I am 

hoping that everyone in the room will join us in

working hard to accomplish the goals set by Dr. Pinn 

to help the Trans-NIH Working Group for Research

on chronic fatigue syndrome (CFS) develop a structure for future research on CFS, at least into one 

type of mechanism that may be operative: neuroimmune mechanisms and chronic fatigue syndrome. 

The principle question is, “Will the understanding 

of central mechanisms enhance the search for 

causes, consequences, and treatment of chronic

fatigue syndrome?”

As laid out by the ORWH and the Trans-NIH

Working Group, the purpose of this meeting is 

to enhance the scientific understanding of CFS by

examining the interface between the brain, the

immune system, and the symptoms of CFS and 

related disorders. In order to accomplish this, we 

needed to bring together basic and clinical scientists from diverse disciplines. Multidisciplinary

description is the language of choice in discussing

how to approach these multisymptom illnesses. 

Why study the central nervous system (CNS) in 

CFS and related disorders? Although I have laid 

out some possible reasons to study the CNS, we 

all have to think broadly, with the help of the 

scientists in this room, to understand whether 

or not this is a reasonable approach.

The etiologies, or triggers and determinants, of 

susceptibility to CFS may be diverse. Some of the 

triggers—for example, chronic stress or genetic or

environmental factors that mold the CNS—may 

alter CNS physiology. The principal symptom of

CFS—fatigue—can be understood in terms of CNS

physiology but may be related to diverse factors, 

including sleep. The effects of cytokines on the 

brain and cortical factors may be involved.

The questions to be explored in this workshop are:

• Can CFS and other related disorders be 

understood as disorders of CNS physiology?

• What methodologies are available to investigate disorders of CNS physiology?

• Are there therapeutic approaches that specifically target CNS physiology that should 

be applied to CFS?

We believe that the topics are relevant to CFS, 

but we need to keep an open mind as to whether 

or not we ought to be studying sleep, stress, and 

other realms of the CNS. We need to keep coming

back to this question: What is CFS? We understand CFS in terms of its symptoms in people. 

As we listen to the basic science and the types 

of methodologies used, we need to keep coming 

back to the patients and the disorder—to understand

how to apply to patients what is being discussed. 

We would like to get a sense from the workshop 

participants whether or not the areas we are discussing are important areas for research, and we 

hope to generate hypotheses for future study. The 

session chairs will summarize the sessions and the 

discussion, so we can all work together to generate

hypotheses that we agree are useful for future research in CFS. The conference format is intended 

to be participatory, and we invite everyone to 

participate fully.

We need to keep coming back 

to the patients and the disorder—

to understand how to apply to 

patients what is being discussed.

Introduction 5

Introduction

Leslie J. Crofford, M.D.

This meeting is multidisciplinary and some 

participants may not be entirely familiar with

all aspects of the definition of chronic fatigue

syndrome (CFS) and previous hypotheses regarding 

its etiology. Therefore, my charge is to define the 

illness, review some of the prior research in terms 

of causative factors, and provide a larger context 

for its discussion.

What is CFS? CFS affects a minority of individuals

who have disabling, long-term fatigue, and hence 

represents only a small part of the much larger world

of fatigued individuals. CFS was first defined in 1994

by the Centers for Disease Control and Prevention,

without an empiric basis, as a condition of debilitating fatigue enduring 6 months in the absence of any

other disorders that could mimic CFS—for example,

untreated hypothyroidism, cancer, rheumatoid arthritis, or psychiatric conditions that have been deemed

exclusionary, such as bipolar illness. In addition, an

individual must exhibit at least four of the following

eight symptoms: problems with short-term memory 

or concentration, sore throat, lymph node tenderness,

muscle pain, poor sleep, migratory noninflammatory

joint pain, new headaches, and post-exertional

fatigue. Those symptoms must have been present

simultaneously for 6 months and must have started

after the onset of the fatigue. This latter criterion was

established because CFS is a syndrome, not a series 

of individual symptoms scattered over time. Lastly, 

it is notable that almost 90 percent of patients with

CFS report that stress worsens their condition, 80

percent gain weight, and 75 percent need a daily 

nap; these symptoms are commonly reported but 

are not part of the case definition.

The fatigue itself also must have certain characteristics. The fatigue is required to have a definite onset

and result in substantial reduction of occupational,

educational, social, or personal activities. The fatigue

cannot be attributable to exercise, insufficient sleep,

or some other factor, or be completely relieved by

rest. As noted previously, no medical or psychiatric

conditions can be comorbid that might explain the

fatigue. The CFS criteria also require that individuals

undergo an evaluation that includes standard laboratory work—for example, a complete blood count,

chemistry panel, and urinalysis—and a complete

physical examination. However, no diagnostic test

and no real markers for CFS exist; CFS is a clinical

diagnosis of exclusion. 

What causes CFS? The thinking in the field is quite

diverse; therefore, the answer to “What causes CFS?”

depends on who is asked. Most people believe that

CFS has multiple causes and that it is a heterogeneous illness. The theories that have been postulated

and investigated in the past 15 years reflect what

patients complain about and the areas of expertise 

of investigators. A variety of different causes have

been postulated. On one end of the spectrum, some

investigators initially believed that CFS was actually

not an illness at all but rather a societal problem 

of labeling, or that physicians were simply taking

financial advantage of patients. On the other hand,

others think that CFS involves multiple chemical 

sensitivities, and that sufferers are simply allergic 

to various environmental agents. Models of CFS 

must take into account expertise in various disciplines and link together research in many areas to

better understand how previously reported abnormalities—or even normal findings—contribute to 

the pathophysiology of illness. 

The answer to “What causes CFS?”

depends on who is asked.

Research during the past 15 years was stimulated 

first by the observation that about 70 percent of 

people with CFS reported that their illness started

with an acute viral or bacterial infection, particularly an upper respiratory or influenza-like illness,

and that they never recovered. As a result, early 

An Overview of Chronic Fatigue Syndrome 7

An Overview of Chronic Fatigue Syndrome

Dedra Buchwald, M.D.
studies focused on viral agents, particularly viruses

that had the ability to be persistent or latent, such as

herpes viruses. Many viral and other microbial agents

have been studied and then discarded as being the primary cause of CFS, although some studies have shown

aberrations in antibody titers and subtle evidence of

infectious agents.

The second wave of research focused on immunologic

findings, triggered by CFS patients’ reports of more

frequent and severe illnesses and longer recovery

times. The hypothesis was that if a primary viral 

or microbial agent did not directly cause CFS, then

perhaps the immune system was not functioning

properly. At least a dozen studies have examined 

various aspects of the humoral and cellular immune

systems. For the most part, these studies observed

decreased natural killer cell function, altered lymphocyte subset number and percent, and a different pattern of activation marker expression in people with

CFS. Although these findings were not detected in 

all patients and all studies, they seemed to be more

reproducible than other immunologic findings.

Any model of CFS must also take into

account diverse published observations

and findings.

The autonomic nervous system was the third major

area of investigation. About 10 years ago, in the

Journal of the American Medical Association, investigators from Johns Hopkins reported on their study 

of whether or not people with CFS were more likely

than normal individuals to have a positive tilt table

test. This test is used to diagnose neurally mediated

hypotension, a form of autonomic nervous system

dysfunction, by measuring blood pressure and pulse.

Investigators found that a significantly greater number of people with CFS had a positive tilt table test

than did healthy controls. Other research on the autonomic nervous system has focused on altered heart

rate variability. Many of the studies of the autonomic

nervous system have been conducted with children.

Since investigations among adults have not consistently replicated the original findings, it remains

unclear how much of a role the autonomic nervous

system plays in CFS.

A fourth area of inquiry has been objective measures

of sleep. Virtually all CFS patients have subjective

sleep problems. On polysomnography, CFS patients

sleep less efficiently, spend more time awake after

going to bed, and have altered stages of sleep. 

In most studies, CFS patients have normal REM

(rapid eye movement) latency, thus differentiating

their sleep from the sleep of patients who have 

major depression.

Recently, a fifth topic of investigation has asked

whether or not a genetic predisposition exists for 

fatigue in general, and more specifically for CFS. 

In a study of 146 pairs of female twins, we found 

that the concordance rate for a CFS-like illness 

among identical twins was 38 percent, but 11 

percent for fraternal twins.1 From this finding we 

infer that there is a familial, if not truly genetic, 

predisposition to fatiguing illnesses. Several other 

studies in the literature support the observation 

of a genetic predisposition to fatiguing illnesses.

Lastly, a theory that has permeated the literature 

since CFS was first described attributes CFS to some

form of atypical depression or another psychiatric 

disorder that has yet to be well defined. The basis 

for this hypothesis was the observation that rates 

of psychiatric disorders among CFS patients are 

three or four times higher than those in the general

population. However, many people with CFS do 

not have a current or lifetime diagnosis; thus, this

model is not fully explanatory. In addition, a lifetime disorder does not explain a current symptom 

or illness. Nevertheless, although psychiatric illness

does not directly cause CFS, the high prevalences 

of psychiatric illnesses must be part of any model 

of CFS. In this regard, research on cortisol and 

ACTH (adrenocorticotrophic hormone) has 

demonstrated that both the levels and the type of

responses were different in CFS patients from those 

in individuals diagnosed with major depression.

Any model of CFS must also take into account diverse

published observations and findings. For instance,

some experts believe that CFS is part of a family of

disorders and that it is not a unique, identifiable disorder. Many demographic and clinical aspects of conditions such as fibromyalgia, irritable bowel syndrome,

and temporomandibular disorder are similar to those

of CFS, although controversy exists about the usefulness of thinking about them as the same condition.

Regardless, CFS models must explain the fact that

these conditions overlap to some extent.

Additionally, studies have detected a variety of biological abnormalities that are not specific for CFS 

and that are not consistently associated with severity

8 An Overview of Chronic Fatigue Syndrome
or type of symptoms. Most of the findings have been

described in isolation from other findings and without

reference symptoms or clinical status. Nonetheless, 

a model of CFS must explain such findings.

A final issue that investigators will need to address 

in designing studies that elucidate a model for CFS 

is the many meanings of the word “fatigue.” Fatigue

is a broad term that should be defined with more

specification. Many kinds of fatigue exist. Fatigue 

has often been classified as physical fatigue and 

mental fatigue, as distinguished from weakness and

sleepiness, which are distinct phenomena. Of note, 

a large study of fatigue in primary care in the United

Kingdom involving 33 million patient years of data

has documented 69 synonyms for fatigue, thereby

demonstrating its multifaceted and heterogeneous

nature (Peter White, personal communication, 2003).

Fatigue results from not having enough sleep, jet 

lag, physical activity, losing a loved one, and being

depressed. For example, if you lose a loved one, you

become depressed and fatigued, but over time you 

get better. What is the physiologic core of recovering?

One model for CFS that directly examines the central

role of fatigue is that persons with CFS “get off the

road and into the ditch” and cannot get back on the

road again. An intriguing approach to CFS would be

to examine how normal people recover from fatigue.

Sleep medicine can discriminate between the physiology

of sleepiness and tiredness related to physical exhaustion. The Multiple Sleep Latency Test consists of a

series of 20-minute nap opportunities used to determine how quickly a person falls asleep, thus providing

an indication of sleepiness. We know almost nothing

about the physiology of fatigue. We can say it is not

sleepiness, but we cannot differentiate types of fatigue

experienced as a response to an adverse task, grieving,

or simple exhaustion. No studies address the physiology of fatigue in pregnancy, although 40 to 50 percent

of women experience considerable fatigue during the

first trimester. This dearth of studies underscores that

we know virtually nothing about perhaps the single

most common class of fatigue among women.

Is neuroendocrine dysfunction the 

cause or the result of physical inactivity?

Many researchers believe that the pathophysiology 

of CFS is not well understood, but most symptoms

and findings can be explained by neuroendocrine

aberrations. We need to focus on models that can 

link mechanism and causation, and studies should 

be designed for this purpose. However, any explanatory or conceptual model of CFS also must explain

diverse observations such as the following:

• Female predominance. In most studies, CFS

affects women more often than men. 

• Acute onset. Most patients describe the onset 

of this illness as occurring over hours or days.

• Uniformity of symptoms. Most people with 

CFS report poor sleep, high stress levels, an

inability to react to stress, pain, psychological 

distress, and a variety of other symptoms.

• Relative absence of prominent findings on 

physical examination. Most CFS patients do not

have objective evidence of an inflamed throat,

enlarged lymph nodes, or muscle weakness. 

• A variety of objective findings across multiple

domains. These findings are present in some 

but not all people.

• Substantial disability. Despite the lack of 

findings on physical examination and lack 

of a diagnostic marker, this illness causes 

substantial disability in most people.

• Altered perception. The literature suggests 

that persons with CFS experience an altered 

perception of effort pertaining to sleep, 

exercise, cognition, and across a variety 

of other domains.

How can we build a model of CFS? We must think

outside the box and, along with conducting traditional

investigations, we must use innovative, creative study

designs and new paradigms, and we must look to

other fields for inspiration, new collaborators, and

other experts for guidance.

What are some examples of investigations that 

contribute to a model for CFS? Using a model in

which neuroendocrine dysfunction is the primary

aberration in CFS, one question might be, “Is neuroendocrine dysfunction the cause or the result of 

physical inactivity?” One way to answer that question is to conduct a case control study that compares the neuroendocrine status of CFS patients 

with healthy, extremely sedentary individuals, such 

as those in traction. Another model-building study

would address the observation that women get CFS

more often than men. Questions of interest might 

be whether female reproductive hormones play a

causative role in CFS or whether use of exogenous

hormones increases the risk for CFS. These questions

could be answered by using epidemiologic data to

An Overview of Chronic Fatigue Syndrome 9
examine the prevalence of CFS in women who are

taking oral contraceptives or hormone replacement

therapy compared to those who are not. 

A third example would be to study the biological

underpinnings of perception and its alteration in 

CFS. One question might be whether there are 

objective measures of perception that quantify the

subjective patient reports of heightened sensitivity 

to noise, visual disturbances, and paresthesias. Scientific investigations using models of disease have tried

to answer these kinds of questions in other conditions.

For example, a case control study was conducted

among students, half of whom were sent to a discotheque and were exposed to loud noises for 6

hours. Subsequently, all the students were put in 

a quiet environment and investigators were able 

to link biological markers to reports of sensitivity 

to noise. In a similar approach, researchers could

compare visual acuity, urinary catecholamines, and

cortisol in CFS patients and control groups in quiet

and stimulated conditions. However, such studies

have not been performed for CFS.

Another interesting paradigm and an example of 

an innovative methodology used the tickle response 

to link external stimuli with internal processing. 

This model also might shed some light on how CFS

patients process information and stimuli. Since the

time of Aristotle, it has been common knowledge 

that you cannot tickle yourself; even though the

motor movement or stimulus is the same, someone

else has to tickle you to elicit the tickle sensation. 

In one study, investigators tickled patients and then

the patients tickled themselves. MRI scans showed

that when patients tickled themselves, the somatosensory cortex did not light up but the cerebellum did;

the opposite occurred when another person tickled

them. The authors concluded that the tickle response

visibly affects the somatosensory cortex if another

person elicits it. However, the absence of predictability makes a person perceive a stimulus as ticklish

and the cerebellum mediates predictability. Investigators then conducted a second experiment in which

they told patients that a machine was tickling them.

By indicating that the machine was going to tickle

them, they were able to prove that it was the element of unpredictability that made a tickle ticklish.

That series of clever experiments examined how 

people perceive and process information. We need 

to describe how CFS patients perceive and process

information, and how this differs from healthy 

people, to better understand this illness.

The challenge is to use this meeting’s collective

expertise to articulate a testable explanatory model

for CFS that focuses on the neuroimmune, hormonal,

and other central nervous system processes in CFS.

This model should include elements from multiple

fields and many domains and disciplines and should

lead to an understanding of the relationship between

objective, scientific, and diagnostic findings and the

symptoms and suffering experienced by CFS patients.

Reference

1. Buchwald D, Herrell R, Hartman S, Belcourt M,

Schmaling K, Goldberg J. A twin study of chronic

fatigue. Psychosom Med 2001;63:936-943.

10 An Overview of Chronic Fatigue Syndrome

The challenge is to use this meeting’s collective expertise

to articulate a testable explanatory model for CFS that

focuses on the neuroimmune, hormonal, and other central

nervous system processes in CFS.
The stress response includes two main arms: the

neuroendocrine stress response and the adrenergic sympathetic nervous system response. The

neuroendocrine stress response includes the hormones

of the hypothalamic-pituitary-adrenal (HPA) axis.

The hypothalamus produces corticotropin-releasing

hormone (CRH), which is the brain stress hormone;

the pituitary gland produces adrenocorticotropic 

hormone (ACTH); and the adrenal glands produce

glucocorticoids. The sympathetic nervous system 

is also activated simultaneously during the stress

response. The peripheral nervous system is another

component of the central nervous system that plays

an important role in regulating immune responses.

Disease results when the regulatory negative feedback

loop of the CNS on the immune system is out of control. Too much activation of the brain’s hormonal

stress response tunes down the immune system and

can lead to infection. Too little activation can predispose the body to inflammation, because the endpoints of the HPA axis on the immune system are 

the glucocorticoid hormones, which are usually

immunosuppressive. However, at lower physiological concentrations, glucocorticoid hormones can 

also be immunostimulatory.

Glucocorticoids regulate immune responses, not 

simply because they are drugs but because they are

the endpoint of the brain’s sensitive hormonal stress

response. This hormonal stress response is set to

respond moment by moment to every change in the

environment. People instantaneously respond to environmental stimuli, or stressors. These changes affect

the immune system through the hormonal cascade, 

and ultimately through the glucocorticoid receptor 

that is part of a family of nuclear hormone receptors.

The glucocorticoid receptors sit in the cytosol, the 

fluid portion of a cell’s cytoplasm, and bind to glucocorticoids. When the hormone binds to the receptor, 

it allows the activated receptor to dimerize, move to

the nucleus, and facilitate translation and transcription of proteins.

Chronic stress is a biological event that results in 

dysregulation of the brain’s hormonal stress response. 

Conditions that have been shown to be associated with

chronic stress include prolonged wound healing (based

on studies done by Janice Kiecolt-Glaser and Ronald

Glaser at Ohio State University), increased severity and

incidence of viral infection (studies by Sheldon Cohen

and colleagues), and decreased antibody production to

vaccine (studies by John Sheridan and colleagues and

Kiecolt-Glaser and colleagues). These sorts of effects

have been shown in chronic caregivers of patients with

Alzheimer’s disease, in situations of marital stress, 

in students undergoing exam stress, and in Army

Rangers undergoing extremes of exercise.

In the case of too little hormonal stress response 

(if the HPA axis is not active enough), the opposite

result occurs: the immune system is tuned up and 

the external hormonal brake to stop out-of-control

inflammation no longer exists. When producing too

little CRH, too little ACTH, and too little glucocorticoids, and when exposed to an antigenic or proinflammatory stimulus, immune cells no longer 

Health Consequences of a Dysregulated Stress Response 11

Session One: The HPA Axis 

Chair: Leslie J. Crofford, M.D.

Health Consequences of a Dysregulated Stress Response

Esther M. Sternberg, M.D.
have a shut-off valve from glucocorticoids. Under

such conditions, the individual may develop autoimmune inflammatory disease. For example, the 

HPA axis hypo-responsive Lewis rats develop many

autoimmune inflammatory diseases, with varying 

patterns according to the pro-inflammatory stimulus to which the rat was exposed. If not exposed 

to such environmental inflammatory triggers, 

Lewis rats live long, healthy lives with no autoimmune inflammatory disease. However, when 

Lewis rats are exposed to streptococcal cell walls, 

lactobacillus cell walls, mycobacterial cell walls, 

or other bacteria, they develop an inflammatory

autoimmune disease that looks like rheumatoid

arthritis. Similar results are seen when Lewis rats 

are given collagen and adjuvant arthritis. When

exposed to extract of spinal cord with myelin basic

protein, they develop a multiple sclerosis-like disease

called experimental allergic encephalomyelitis (EAE).

Depending on the nature of the pro-inflammatory

trigger to which they are exposed, Lewis rats can

develop autoimmune myasthenia gravis, experimental sialadenitis, experimental autoimmune thyroiditis, adrenalitis, uveitis, orchitis, myocarditis, 

or nephritis. Thus, many animals with a predisposition to autoimmune disease will not develop 

disease until they are exposed to an environmental

trigger, and the nature, dose, and route of exposure

all contribute to development of disease.

A blunted HPA axis is only one factor determining whether an individual animal or organism will

develop chronic autoimmune inflammatory disease

after exposure to an antigenic or pro-inflammatory

stimulus. Other factors, including genetic predispositions and other hormonal factors, play an 

important role in the development of autoimmune

disease. Sex hormones, their receptors, and the 

hypothalamic pituitary gonadal axis all play a 

critical role in the development of autoimmune

inflammatory diseases. Thus, females of most 

species have a higher incidence and/or severity 

of most autoimmune inflammatory diseases. For

example, female-to-male ratios are 10:1 for lupus, 

2:1 for rheumatoid arthritis, and in the 2:1 to 

10:1 range for other similar diseases. Autoimmune

diseases are multigenic and polygenic—many genes

control them, each with a small effect. More than 

20 different regions on 15 different chromosomes

determine susceptibility and resistance to inflammatory arthritis.

Fischer rats are closely related to Lewis rats; about 

66 percent match across the genome, and the two

strains are histocompatible. However, Fischer rats 

are resistant to developing the same autoimmune 

diseases in response to the same dose, route, and 

type of pro-inflammatory triggers. Early studies 

found a high inflammatory response to carrageenan,

an innate trigger, in Lewis rats and virtually no such

response in Fischer rats. Lewis rats exhibit blunted

corticosterone, ACTH, and CRH responses, compared to Fischer rats that show a hyper response 

in all cases.

Female-to-male ratios are 10:1 for

lupus, 2:1 for rheumatoid arthritis,

and in the 2:1 to10:1 range for other

similar diseases.

Similarly, these two strains of rats behave differently in response to stress. This is not surprising:

CRH is not only a neuroendocrine hormone that 

acts peripherally on the immune and other systems 

in the body, but it is also a neuropeptide that is

expressed throughout the brain and plays an important role in stress behaviors. A Lewis rat placed in 

the novel environment of an open field will run

around and explore in a relaxed manner; a Fischer 

rat in a novel environment will exhibit stress behaviors, including decreased locomotion, freezing,

grooming, and rearing. These findings do not mean

that one rat strain is less stressed than the other or

that they are exposed to different amounts of stress.

The findings mean that the rats are more or less

responsive to a stressful situation, most likely in 

part because of the difference in stress hormone 

levels in the brains.

The concept of an association between a blunted 

HPA axis response and susceptibility to autoimmune disease crosses species and diseases. A blunted

HPA axis response is shown by chickens with thyroiditis and scleroderma; some strains of mice with

lupus; rats with other illnesses besides arthritis such

as experimental allergic encephalomyelitis, septic

shock, inflammation, and others; and humans with

rheumatoid arthritis, lupus, Sjögren’s syndrome, 

dermatitis, asthma, fibromyalgia, CFS, and irritable

bowel syndrome.

12 Health Consequences of a Dysregulated Stress Response
Clinical studies of Sjögren’s syndrome, lupus, dermatitis, and asthma have found that the blunting 

may be present at different points in the HPA axis 

or with different patterns, but the dysregulation 

of the axis exists in all these conditions. Without

being exposed to a stressful stimulus, the differences

between the two strains of rats—or any two humans—

are not evident. The response is individual, but the

stress hormone axis must be stimulated in order to

distinguish among the high and low responders. 

The axis can be turned on with administration 

of hormones of the stress response, such as intravenous ovine CRH, by inducing hypoglycemia, 

or with psychological stressors, such as public 

speaking and mental arithmetic.

Genetic interruptions of the HPA axis (as in Lewis

rats), surgical interruption in animal models of the

axis (by removing the pituitary or the adrenals), or

pharmacological interruptions (by blocking the glucocorticoid receptor with drugs) all tend to predispose

to worse inflammatory disease. Even in inflammatoryresistant strains, such as Fischer rats, when the axis is

blocked pharmacologically or surgically, the inflammatory-resistant animal will become so susceptible 

to inflammation that it will die within the first 12

hours of exposure to a pro-inflammatory stimulus,

such as bacterial cell walls.

The concept of an association 

between a blunted HPA axis response

and susceptibility to autoimmune 

disease crosses species and diseases.

We demonstrated this effect using RU486, a progesterone receptor antagonist and also an equally

potent glucocorticoid receptor antagonist. Neither

RU486 alone nor streptococcal cell walls alone 

have any effect in Fischer rats. Combined, however,

some of the rats died rapidly in septic shock and 

the surviving animals developed arthritis. The effect

was reversed with corticosterone. Other researchers

have shown similar effects in otherwise inflammatory

disease-resistant animals whose HPA axis was interrupted by adrenalectomy, hypophysectomy, or treatment with glucocorticoid receptor antagonists. In

these studies, ordinarily resistant animals with EAE,

or those exposed to salmonella, Shiga toxin, or

murine cytomegalovirus developed shock with a 

high incidence of mortality. These animal studies

demonstrate that if the HPA axis is blocked at any

point and in any way (at the level of the adrenals, 

the pituitary gland, or the glucocorticoid receptor), 

an inflammatory-resistant animal will become 

highly susceptible to inflammation and potentially 

to the lethal effects of shock. Reconstituting the 

axis with glucocorticoids or by hypothalamic transplants, as in studies in Lewis rats, can reverse the

process. In this latter case, inflammatory-susceptible

Lewis rats became resistant to inflammatory disease

when they received Fischer hypothalamic transplants,

at the same time that their HPA axis responsiveness

was corrected. 

Researchers have also studied why Lewis rats 

have a blunted CRH response. A number of 

neuropeptide/neurotransmitter systems are differentially regulated in inflammatory-resistant and

inflammatory-susceptible rats. It is difficult to 

discern which is cause and which is effect, but 

multiple systems that regulate the immune system 

are dysregulated. CRH is blunted, but so is the 

sympathetic nervous system response.

Studies conducted a number of years ago looked 

at noradrenergic responses in Lewis and Fischer 

rats in response to hypoglycemia. A blunted sympathoneuronal response was observed in the Lewis

rats compared to the Fischer rats, suggesting the 

following important issues: 

• The sympathetic nervous system innervates

immune organs such as the spleen. Spleen cells

are in close apposition to the noradrenergic 

nerve terminals. There is regional regulation 

of immune organs—such as the lymph nodes,

spleen, and thymus—by the sympathetic 

nervous system.

• Neuroanatomically, investigators want to 

know why there is a dual dysregulation of 

the HPA axis—CRH in the hypothalamus and

sympathetic responses. Dr. Sternberg’s studies

have looked at the distribution of CRH mRNA 

in the two strains of rats and have found that 

it is not that the Lewis rats do not make any 

of the brain stress hormones, but rather that 

they make it in different distributions. A threedimensional reconstruction of serial sections 

in the Lewis rats shows a part missing paraventricular nucleus of the hypothalamus, an

expression of CRH in the part of the brain 

Health Consequences of a Dysregulated Stress Response 13
that projects to the autonomic nervous system. 

It is possible that in Lewis rats there is a dual

blunting of these two important arms of the 

hormonal stress response and the neuronal 

stress response that may be related to some

regional cellular dysfunction at the level of neurons that connect the two systems within the

brain. This theory merits further explanation.

Complex autoimmune inflammatory diseases are 

regulated by many genes, each with small effect—

thus they are polygenic and multigenic. Genetic 

linkage and segregation studies in Lewis and Fischer

rats showed two regions on two different chromosomes that link to the inflammatory susceptibility 

and resistance of these two strains of rats. These 

2 regions exactly superimposed on 2 of the more 

than 20 different regions on 15 different chromosomes that many other researchers have shown to be 

associated with inflammatory arthritis. These findings

have important implications in complex illnesses such

as CFS. The familial tendency of CFS is well known.

If an individual inherits all 20 of the regions associated with inflammatory susceptibility, as do Lewis rats,

there is a high probability that, like the rats, this 

individual will get an inflammatory disease when

exposed to inflammatory triggers in the environment.

If, on the other hand, like a Fischer rat, a person

inherits few of the susceptibility regions or inherits

inflammatory-resistance genes, she or he is far less

likely to contract an inflammatory disease, even

when exposed to inflammatory triggers. Thus, in 

complex diseases, it is important to remember that

there are many regions on many chromosomes that

contain many genes that predispose to these kinds 

of illnesses, and there is a genetic dose effect of the

number of these regions inherited.

The next question to explore is what candidate 

genes are in these linkage regions. Rat chromosome

10 is identical to a region on human chromosome 17

that links to many autoimmune diseases. It contains 

a number of genes that regulate both the neuroendocrine stress response and inflammation. Looking 

at two of these genes, we found no difference in the

coding region on the CRH type 1 receptor and believe

there also is no difference in the promoter region,

because there is no difference in regulation of these

receptors in the two strains. Angiotensin-converting

enzyme is another gene present in the chromosome 

10 linkage region that regulates both CRH and

inflammation, but it is unlikely that that mutation

contributes to the trait.

The important message of these studies is that the

genetic contribution to the variance in the inflammatory trait in this model is low (approximately 35

percent), compared to the environmental contribution

(approximately 65 percent). Similarly, in conditions

such as diabetes, cardiovascular disease, hypertension,

inflammatory arthritis, lupus, and multiple sclerosis,

the variance in the trait contributed by genotypic 

factors typically is only between 35 and 40 percent.

For the geneticist, this means it will be difficult to

find the gene or genes that predispose to these traits.

However, newer technologies are now available to

examine many potential candidate genes simultaneously. We looked at gene expression microarrays 

to determine how patterns of gene expression may

differ in different individuals or groups. Studying 

the Lewis and Fischer rats exposed to the proinflammatory stimulus lipopolysaccharide (LPS), 

we surprisingly found few genetic differences—

only five genes that are differentially expressed 

in the hypothalamus in the two strains of rats. 

Three of the genes are unknown expressed 

sequence tags. The other two are transthyretin 

(TTR), a thyroid hormone transporter, and 

cholecystokinin (CCK), both of interest in this 

context. Future studies will look at whether differential thyroid hormone axis regulation could

explain some of the differential CRH and HPA 

axis responsiveness differences in these strains, 

a complicated investigation because it is difficult 

to know whether the HPA axis change is predisposed to the thyroid hormone changes or 

vice versa.

The important message of these 

studies is that the genetic contribution

to the variance in the inflammatory 

trait in this model is low (approximately

35 percent), compared to the environmental contribution (approximately 

65 percent).

When considering CFS, the finding of differential 

TTR is of interest because people who have hypothyroidism experience fatigue. Perhaps an area for future

exploration should be interactions between multiple

14 Health Consequences of a Dysregulated Stress Response
hormone axes, at least examining axes with secondary roles that could be amplifying or contributing 

to a problem. 

The finding that only 35 percent of the variance

comes from genetic factors and 65 percent comes

from environmental factors can be viewed as a 

positive finding for implications in managing 

complex diseases such as arthritis, because 

environment can be more easily controlled than

genetics. One environmental factor that has been

studied is maternal behavior and maternal-pup interactions in rats. In examining maternal behavior, 

we found that Lewis rats with a blunted HPA axis

response had a rapid retrieval rate of their pups,

while the Fischer rats completely ignored the pups 

for the entire 15 minutes of the test time in which

pups are separated from the mother around the 

edge of the cage. The Lewis mothers picked up 

their pups, put them in a corner, crouched, and

nursed them within 3 minutes of separation while 

the Fischer mothers groomed themselves and ran

around, ignoring the pups and displaying stress

behavior. Cross-fostering studies, where mothers 

of the different strains adopt and raise the opposite pups indicate that strain, gender, and maternal

environment interactions determine adult stress

responsiveness in this model.

If this happens in the wild or in the laboratory 

setting, what happens to the offspring? During 

the past 25 years, studies have found that separation of rat pups from their mothers for as little 

as 5 to 15 minutes a day for the first 2 weeks of 

life result in a permanent increase in HPA axis

responsiveness that lasts through adulthood. 

Many factors contribute to this increase. Some

involve temperature, but even when researchers 

control for temperature and thyroid hormone

responses, animals still were left with a permanent change in the stress axis. Thus, the stress 

hormone axis is plastic, and there are critical 

periods in development when it can be changed. 

What is not known is whether there are also 

critical periods in adulthood when the responsiveness of the stress axis can be changed, how 

much it might be changed in adulthood if at all, 

and exactly how these animal findings can be 

extrapolated to humans. It is known from human

studies in adopted Romanian orphans who experienced extremes of deprivation, malnutrition, and 

illness in early infancy that adoption into Canadian

families before the age of 9 months was associated

with relatively few sequelae, whereas some deleterious effects were seen in infants adopted after 

the age of 9 months. It is likely, therefore, that in 

humans far greater degrees of early environmental

stress may be required to permanently affect the 

stress hormone axis than in rodent models. Nonetheless, these are areas of research that need to be

addressed to understand factors contributing to 

dysregulated stress hormone responses in complex 

illnesses, including arthritis and CFS. 

Another level at which the stress hormone axis can 

be dysregulated is at the level of the glucocorticoid

receptor. In rheumatoid arthritis, and to a lesser 

extent in lupus, there are glucocorticoid receptor

polymorphisms in the glucocorticoid receptor-beta,

which is thought to be a dummy form of the glucocorticoid receptor that could act as an endogenous

glucocorticoid receptor antagonist. The receptor has

been shown to be elevated in several autoimmune,

inflammatory, and allergic diseases (e.g., irritable

bowel syndrome and asthma). This mutation is 

associated with increased receptor mRNA stability and increased receptor levels. Alternatively, it 

is possible that in some individuals with these 

illnesses, problems may occur at the level of the 

hypothalamus or sympathetic nervous system as 

in Lewis rats, in the pituitary, the adrenals, or the 

glucocorticoid receptor. In all cases, some degree 

of glucocorticoid resistance would result and, 

wherever the interruption occurs, it will predispose an individual to enhanced susceptibility and

severity of inflammatory disease when the individual is exposed to inflammatory triggers, because 

of a lack of anti-inflammatory, immunosuppressive

effects of glucocorticoids.

In summary, these illnesses must be considered at 

multiple levels. Multiple genetic factors predispose 

the body to these illnesses. Potentially, developmental factors can contribute to the onset of illnesses.

Environmental exposures are also probably necessary to trigger such illnesses. The hosts’ responses 

to all of these factors depend on the set point of 

multiple host response systems. This applies to 

neural (autonomic) responses, the neuroendocrine

(HPA, hypothalamic-pituitary-thyroid [HPT])

response systems, and the sex hormones (hypothalamic-pituitary-gonadal [HPG] axis). After an 

Health Consequences of a Dysregulated Stress Response 15
individual is exposed to environmental factors—

viral, bacterial, or inflammatory—all of these 

hormonal and neural factors together contribute to determine whether an individual recovers

quickly or has persistent symptoms. In studying 

CFS, it will be critical to focus not only on environmental triggers but also on the resiliency of 

the host’s response systems in returning to baseline.

Everyone is exposed to triggers, but some individuals’

response systems quickly return to baseline while 

others take a much longer time or never completely

recover, and it may be this factor as much as the

nature of the initial response that determines the 

ultimate outcome of a disease.

16 Health Consequences of a Dysregulated Stress Response

In studying CFS, it will be critical to focus not only on

environmental triggers but also on the resiliency of 

the host’s response systems in returning to baseline.
About 4,500 years ago, the Nei Ching, the

ancient Chinese classic on internal medicine,

listed nine groups of disease-causing agents.

The list included the emotions as potential causative

factors in disease, stating that worry and imagination

can upset the functioning of the spleen. In many ways,

this sums up what the field of psychoneuroimmunology is trying to understand today. Wondering how

different mental and emotional states can affect

health is not a monopoly of the ancients. Cover 

articles of many popular magazines today deal 

with stress, indicating how much this subject 

occupies modern thinking. 

Stress can be defined as a constellation of events 

that begins with a stimulus (the stressor), which 

precipitates a reaction in the brain (stress perception),

which then results in the activation of fight-or-flight

systems in the body (the physiological stress response).

Stress is defined in the following broad categories:

• Acute stress lasts for minutes to hours 

in duration.

• Chronic stress persists for weeks, months, 

or years and involves a dysregulation of the 

circadian rhythms, leading to well-known 

deleterious consequences.1

The activity of the hypothalamic-pituitary-adrenal

(HPA) axis is one example of a psychophysiological

stress response. A stressor could be a prototypical

danger stimulus, but it could also be a prototypical

excitatory stimulus, such as a first kiss on a first date,

which may not often be regarded as a stressor but

which often activates the same types of stress axes. 

A stress perception in the brain results in a physiological stress response. The HPA axis response results in

the ultimate elaboration of glucocorticoid hormones

that signal to the rest of the body that something is

happening or is about to happen.

The HPA axis is not the only stress response system.

Many other systems involve the release of epinephrine, norepinephrine, endogenous opioids, prolactin,

cytokines, and other hormones during a physiological

stress response. (Most of the work from our laboratory has been mediated by epinephrine and cortisol.)

While it is possible that other hormones contribute 

to these effects, none have yet been found to equal 

the significance of cortisol and epinephrine.

A poster from the National Library of Medicine

describes stress as “a loaded gun,” and goes on to

state, “If left untreated, stress can kill you, just as

surely as a bullet. Do not wait for the gun to go off.

Get help today.” There is validity to this claim, but

there are other ways to consider it. First, it need not

necessarily or always be the case that stress is harmful. Second, while a loaded gun can kill if used

unwisely or if in the hands of an enemy, a loaded 

gun can also protect if it is used effectively.

Just as the stress response prepares the cardiovascular, musculoskeletal, and neuroendocrine systems for

fight-or-flight, it may also prepare the immune system

for challenges, such as wounding or infection, that

may be imposed by the actions of a stressor. In other

words, short-term stressors may enhance immune

function within compartments, such as the skin, 

that are likely to be compromised by the actions of 

a stressor, such as a predator.2 Without a full-blown

efficient psychophysiological stress response, a predator has little chance of capturing its prey and hence

feeding itself and surviving. Similarly, without a fullblown psychophysiological stress response, the prey

has little chance of surviving and escaping the predator. An efficient psychophysiological stress response

gives both predator and prey the chance to survive.

This leads to the fundamental principle that the 

psychophysiological stress response is a crucial 

evolutionarily conserved survival system.

Stress and the Augmentation of Immune Function 17

Stress and the Augmentation of Immune Function

Firdaus S. Dhabhar, Ph.D.
The central goals of the research in my laboratory are:

• To identify the cellular, molecular, and physiological mediators of nature’s survival systems, 

the successful stress response.

• To harness these mediators to maintain health 

or to restore health in case of disease.

• To figure out ways to intervene in situations 

in which nature’s survival system may itself 

contribute to pathology.

To reconcile the different views of stress, stress can be

viewed as a spectrum of possibilities. At one end of

the spectrum is acute stress, what Hans Selye labeled

“eustress.” Eustress involves brief duration stressors

of 1/2 to 21/2 hours and a normal circadian rhythm. 

It is an adaptive response and involves an enhancement of immune function in certain compartments. 

At the other end of the spectrum is chronic stress, 

or distress, which is prolonged or repeated in nature,

involves a dysregulated circadian cortisol rhythm, is a

maladaptive response, and is well known to suppress

immune function. Many researchers have looked at

this aspect of chronic stress and immune suppression.

Of interest is the part of the spectrum representing

resilience, as it takes a significant amount of loading on biological systems before they move from the

adaptive end of the spectrum to the pathological end.

We use restraint, novelty, and social conflict as 

stressors in our animal studies. These are naturalistic,

brief, non-painful, non-severe stressors that generate

physiological stress responses. In clinical studies, the

process of undergoing surgery (knee and oral) is used

as a stressor as well as the Trier Social Stress Test

(TSST), in which subjects are challenged with mental

arithmetic problems and public speaking. The goal 

of these experimental models is to simulate the 

fight-or-flight stress response. Results of one TSST

study that examined hormones in the bloodstream

after arithmetic and public speaking challenges 

found that different people mount different degrees

of stress response. In one subject, for example, 

there was an ACTH response in the plasma about 

20 minutes after the challenge, a cortisol response,

and a norepinephrine response.

In animal and human studies, what happens to

immune cell numbers in the bloodstream during 

acute stress? Understanding of the meaning of 

these changes remains preliminary. What is seen 

is a redistribution of the body’s “soldiers,” or 

immune cells, during acute stress, so that these 

soldiers are moving from their barracks into 

the boulevards and onto battle stations.3,4 These 

military analogies mean that in the early phases 

of a stress response, immune cells mobilize from 

“barracks”—organs such as the spleen and the 

bone marrow—into the bloodstream (the boulevards), registering as an increase in lymphocytes 

and monocytes in the blood. As the stressor progresses, there is a decrease in lymphocyte and 

monocyte numbers in the bloodstream, which 

was once perceived as a net loss of cells in the 

body. More than 50 percent of the circulating

immune system is lost during acute stress, which 

is one of the reasons this type of stress was once

thought to be immunosuppressive. However, researchers have found that this decrease in immune

cells in the blood does not represent a net loss of 

cells from the body, but rather redistribution of 

cells from the bloodstream to organs such as the 

skin and the lymph nodes, and perhaps the gastrointestinal and urogenital tracts. The skin and lymph

nodes have been identified as critical targets—the battle stations—to which leukocytes are known to traffic

during an acute stress response. Neutrophils behave

slightly differently than lymphocytes and monocytes,

but still in agreement with the central hypothesis.

In examining functional consequences of this redistribution of leukocytes to the skin and skin-draining

sentinel lymph nodes during acute stress, researchers

are looking at whether this activity increases the 

ability of an organism to mount immune responses 

in the skin following an acute stress response. Several

different animal models, as well as human studies, 

are used to test functional consequences. A woundhealing model and a cell-mediated immunity model

are being studied in humans and animals.

18 Stress and the Augmentation of Immune Function 
The cell-mediated immune model enables researchers

to tackle different angles of these functional consequences. The hypothesis being tested is that acute

stress experience before antigen exposure will enhance

the ensuing immune response. To test this hypothesis,

the skins of control and acutely stressed animals were

exposed to antigen and then examined for differences

in immune response. An increase in pinna thickness, a

measure of a gross integrated immune response much

like a physician measuring the increase in diameter 

of a tuberculin skin test, was seen in a group of nonstressed animals whose skin was exposed to an antigen. The animals mounted a prototypical immune

response that peaked at about 24 to 48 hours, similar

to a classic poison ivy delayed-type hyposensitivity

response. A cross-section of skin exposes the stratum

corneum, epidermis, dermis, striated muscle, and cartilage. A sample taken 24 hours post-stress exposure

revealed a massive leukocyte infiltration (visible as

blue dots with a hematoxylin eosin stain) moving to

the stratum corneum, as predicted, because the antigen was administered on the top surface of the skin.5

The infiltration peaked about 24 to 48 hours after

antigen administration.

The immune response from animals that were stressed

a single time for 2 hours before an antigen was placed

on their skin occurred at a faster rate, attained a higher peak, and remained significantly elevated compared

to the immune response of the non-stressed animals.

Histological sections compared at exactly the same

time showed a much more vigorous immune response

in the animals that were acutely stressed before receiving the antigen, with a significantly larger number of

leukocytes and distention or swelling of tissue.5 Other

immunocytochemical markers indicated not only that

more cells were coming into the site of the acutely

stressed animal that had been challenged, but also

that these cells showed a more activated profile, 

as measured by some of their activation markers.

This response has been observed in a number of 

different models, including mice, hamsters, rats, and

nonhuman primates, and in some human studies. In a

study of patients with post-traumatic stress disorder

(PTSD) due to childhood abuse, we found enhanced

delayed-type hypersensitivity (DTH) response, as in

the animal model.6 Several potential mechanisms 

are being explored to mediate this effect, including

enhanced acute stress reactivity that PTSD patients

are known to have. Other potential mechanisms are

enhanced levels of pro-inflammatory cytokines that

PTSD subjects often show and decreased levels of

basal cortisol that have been observed in some PTSD

cases. In this study, no differences in basal cortisol

levels between controls and PTSD subjects were 

seen. The implication of this study may be that the

enhanced immune reactivity seen in PTSD plays a

part in mediating the greater number and frequency

of inflammatory disorders reported by PTSD patients.

Whereas acute stress enhances 

immunity, chronic stress suppresses 

the immune response.

A number of other studies that examined infection,

wounding, and antigen-specific responses concluded

that acute stress enhances both innate (primary)

immune responses and adaptive (secondary) immune

responses. The mediators of the immuno-enhancement

are physiological concentrations of epinephrine and

corticosterone, which are mediating the immunoenhancing effects of acute stress.

Stress-induced enhancement of immune function 

can be protective, as in the case of wound healing 

or resistance to infection. However, stress-induced

enhancement of immune function can also have

pathological effects. Examples are cases of exacerbating allergic or inflammatory reactions of autoimmune diseases, which might include CFS. Many

CFS patients say stress worsens their condition. If

there is an inflammatory etiology to CFS, it is possible that it might be part of the mechanism by which

stress exacerbates some of the inflammatory components of the syndrome, thereby worsening symptoms.

We have also tested the hypothesis that, whereas

acute stress enhances immunity, chronic stress suppresses the immune response. Several studies have

confirmed this hypothesis. In one study of chronically

stressed animals, skin-cell-mediated immune response

time was slower than in a control group; in another,

chronic stress administered before antigen exposure

significantly suppressed the immune response. 

Circadian rhythms also play a role. A Swahili proverb

states: “Every morning a lion wakes up knowing that

it has to outrun the slowest gazelle or it will starve.

Every morning a gazelle wakes up knowing that it 

has to outrun the fastest lion or it will die.” The moral

of the story is that whether one is a gazelle or a lion

or even a human, one must be ready to run every

morning. The relevance to the current discussion 

is the relation of circadian rhythms to the immune

Stress and the Augmentation of Immune Function 19
system. An internal alarm clock gets people—and

lions and gazelles—ready to run every morning. This

alarm clock taps into the same hormonal access as 

the stress axis. Just as activating the HPA axis during

stress can trigger cortisol secretion, the HPA axis is

also influenced by the circadian rhythm. At the beginning of the active period of the diurnal cycle, there 

is an increase in cortisol or corticosterone levels, and

near the end of the active period of the diurnal cycle

there is a decrease. This presents a natural phenomenon against which to test findings with acute stress.

Based on acute stress studies, we predicted that 

blood lymphocyte and monocyte numbers would

decrease when corticosterone levels increased, that

skin leukocyte numbers would go up at the same 

time (as they do with acute stress), and that a skin

immune response would show enhancement if the

animals or humans were challenged on the skin at 

the beginning of the active period of the diurnal cycle.

Real time data of the corticosterone rhythm found

that when corticosterone levels rose at the beginning

of the active period, leukocyte numbers fell. When

corticosterone levels fell, leukocyte numbers rose, a

result that has been reported by many researchers.

Another prediction, based on the acute stress studies,

was that challenging the skin of an organism at the

beginning of the active period of the diurnal cycle,

when leukocyte numbers in the blood are lowest,

would find leukocyte numbers in the skin at their

highest, with a larger immune response for an 

active period challenge. 

In the Stanford breast cancer studies, some subgroups

of patients showed normal circadian cortisol rhythms

and some were dysregulated. In the normal rhythm

patients, cortisol was high in the morning at the

beginning of the active period and low in the evening.

In the dysregulated patients, cortisol was basically

flat, starting out high in the morning and staying high

through the evening. The dysregulated diurnal cortisol

rhythm appeared to be correlated with increased mortality in these patients, pointing to significant consequences of a regulated or normalized rhythm.7

Animal studies enable researchers to examine how

one might dysregulate the cortisol rhythm with a

chronic stress load. In one study, a mild stressor was

repeated for 1, 3, and 5 weeks. As the chronic stress

load was increased, the normal low level of corticosterone that would be expected at the beginning of 

the inactive period increased. The chronic stressor

increased the diurnal trough corticosterone levels 

and flattened the circadian corticosterone rhythm.2

The different parameters of CFS suggest possible

causes, including infection causing a chronic 

subthreshold immune activation, physiological 

dysregulation, endocrine dysregulation, circadian 

dysregulation, or sleep dysregulation. However, it

might be difficult to differentiate between cause and

consequence, and results of any of these dysregulations can contribute to other dysregulations and 

feed into CFS. Several mediators may be involved—

activated immune cells, cytokines, hormones, 

neurotransmitters, or other yet-unknown factors.

Stress can have important effects on any of these

activities, and it can also have an effect through 

the described mechanisms. There are many ways 

in which stress, either intrinsic or extrinsic, might

affect the progress or the nature of CFS. The fact 

of having CFS itself might affect a patient’s stress

load. The interrelated nature of issues associated 

with CFS emphasizes the need for multidimensional,

multifactorial approaches, and that hypothesisdriven studies might also be useful in understanding relationships of the factors and determining 

cause versus effect.

Discussion

Dr. Buchwald: Many aspects of CFS invoke an 

explanation using your chronic stress model, and 

others are more reminiscent of your acute stress

response. For example, many CFS patients report 

that they have been under chronic stress just prior 

to the onset of illness. A number of individuals also

report various kinds of victimization and trauma

early in childhood or in their adult life, and most 

people who are studied are chronically ill at the 

time of the study. There are also various more acute

aspects to the illness—for example, the acute onset,

the impaired response to acute stressors (by selfreport), and exacerbations of the illness itself. 

How would you parse out those effects in studies 

of CFS or, alternatively, what might you expect to 

see in studies on stress and augmentation of the

immune response?

Dr. Dhabhar: In general, it seems that the acute stress

system is tapped to enhance the immune response that

is commanded by the antigen-presenting situation at

the time the stressor is experienced. Some responses

20 Stress and the Augmentation of Immune Function 
benefit from or are enhanced by having an IL-2 

interferon gamma response, and the acute stressor 

can enhance them. In diseases like CFS and many

pro-inflammatory disorders, the IL-4/IL-10 driven

immune responses may be the problem. One might

ask whether in CFS acute stress drives up IL-4/IL-10

and, if so, how? One might also ask at what point is

the ability to mount these responses lost, relative to

an increasing and immunosuppressive chronic stress

load? In a study that explains the phenomenon of

burnout in shift-working nurses, it was found that,

after a point and because of the exceeded chronic

stress load, there is no acute stress response. Perhaps

CFS is a case of the acute stress response gradually

being lost in favor of a more chronic stress load.

Other evidence is that the chronic stress load seems to

push the IL-4/IL-10 response, which has a reputation

of producing more immunopathological reactions.

References

1. Dhabhar FS, Satoskar AR, Bluethmann H, David

JR, McEwen BS. Stress-induced enhancement of

skin immune function: a role for IFNγ. Proc Natl

Acad Sci U S A 2000;97:2846-2851.

2. Dhabhar FS, McEwen BS. Acute stress enhances

while chronic stress suppresses immune function

in vivo: a potential role for leukocyte trafficking.

Brain Behav Immun 1997;11:286-306.

3. Dhabhar FS, Miller AH, Stein M, McEwen BS,

Spencer RL. Diurnal and stress-induced changes

in distribution of peripheral blood leukocyte subpopulations. Brain Behav Immun 1994;8:66-79.

4. Dhabhar FS, Miller AH, McEwen BS, Spencer

RL. Effects of stress on immune cell distribution—dynamics and hormonal mechanisms. J

Immunol 1995;154:5511-5527.

5. Dhabhar FS, McEwen BS. Stress-induced

enhancement of antigen-specific cell-mediated

immunity. J Immunol 1996;156:2608-2615.

6. Altemus M, Cloitre M, Dhabhar FS. Cellular

immune response in adult women with PTSD

related to childhood abuse. Am J Psychiatry 2003

in press.

7. Sephton SE, Sapolsky RM, Kraemer HC, Spiegel

D. Early mortality in metastatic breast cancer

patients with absent or abnormal diurnal cortisol

rhythms. J Natl Cancer Inst 2000;92:994-1000.

Stress and the Augmentation of Immune Function 21

Evaluating Immune Function in CFS 23

One of the most significant problems in evaluating immune function in CFS occurs because

all CFS patients are often grouped together

under one large umbrella when, in fact, the population is heterogeneous. Subpopulations must be

defined, but investigators have not agreed on those

definitions. To date, the problem has been either

ignored or individual researchers have defined subpopulations for the purposes of their studies. If cases

are classified by underlying dysfunctional systems,

broadly overlapping circles of immune, autonomic,

and HPA axis dysregulation are seen, but researchers

do not know the extent of overlap. Scientists lack the

tools, the consensus, and the empirical data needed 

to create the definitions that would allow research 

to move forward more quickly and with consistency.

Hundreds of papers have explored immune dysfunction in CFS, with much attention to cytokine dysregulation. Type 1 or type 2 cytokine patterns are often

referred to as IL-4/IL-10, the pattern that would be

predicted in a chronic stress model. The literature is

replete with papers that describe type 2 dysfunctions

and pro-inflammatory cytokine expression in at least

some subpopulations of CFS. Considering the meaning of these patterns in the context of cytokine dysregulation, type 1 cytokines enhance natural killer 

cell function. The natural killer cell function has 

been described as subnormal in CFS patients, so 

this is a plausible conclusion. 

Subpopulations must be defined,

but investigators have not agreed 

on those definitions.

Type 1 cytokines are needed for T cells to interact

appropriately and grow in culture, and lymphocyte

proliferation data suggest that this does not function

as it should in some people with CFS. Type 2 dysfunction tends to be associated with humoral factors,

specifically immunoglobulin E (IgE) production, 

which creates allergies and sets up subsequent antibodymediated dysfunction and autoimmune consequences.

A number of research issues became evident in a

review colleagues and I conducted of more than 100

papers on immune abnormalities published in the 

past 2 decades by 44 different research groups. 

Case definitions have changed over time although

since 1994 there has been widespread use of the 

international case definition of 1994 (the Fukuda 

criteria). We weighted our assessments by the number 

of relevant papers and the consistency of findings.

In reviewing immune activation data, it is necessary

to view the whole body as a three-dimensional or

over-time description of the process of immune activation. For example, when considering the RNA cell

interferon induction pathway, the focus is on intercellular events that will eventually result in some 

cell membrane expression downstream that enhances

the cell function, and on peptides produced by the 

cell that would circulate in the serum. However, 

comparisons have been difficult because researchers

have used a number of different methods to try to

define the state of immune activation. Other evidence of immune activation finds that naive cells 

tend to be present in larger numbers in a less activated patient, and once activated they become 

memory cells. Memory cell population in higher 

Evaluating Immune Function in CFS

Nancy Klimas, M.D.
numbers in people with CFS has been shown by 

four groups (413 patients in one set of studies 

and 71 in another), with some dissenting studies.

Immune activation can be studied with several different markers. Literature covering approximately 3,000

patients supports the finding that immune activation

markers have been found in higher numbers in CFS

patients than in control populations. Some of those

markers include:

• CD38 is a specific marker for a particular type 

of cellular activation. It has been described by 

a number of groups.

• CD28, using a marker on the suppressor 

T cell, has been the subject of fewer studies.

Natelson’s research found CD28 in one group 

of subjects and not in others, illustrating that 

different results are seen even within a single

research site.

• CD26 is a marker that may be associated with

symptom severity. An ongoing study of the use 

of cognitive behavioral therapy (CBT) looks at

immune markers as they relate to markers for

severity of illness; results indicate that the immune

markers, particularly CD26, correlate with flulike and fatigue symptoms.1 The correlations are

strengthening as the study continues. Two CBT

studies of two different CFS patient populations

have confirmed the association of CD26 with 

illness severity, and when that is weighed with

low natural killer cell function, the association 

is even stronger.2,3

• Neopterin is inexpensive, in serum (therefore 

easy to use), and without the need for flow 

cytometry. Although not as sensitive a marker 

as the flow markers and not as reliable, it still 

has some usefulness in clinical studies. In one

study, high neopterin was not found in a CFS 

population until a severity of illness split was 

done. After that split, investigators found high 

levels of neopterin in CFS patients with high 

cognitive difficulties, but not in people without

cognitive complaints. This finding underscores 

the importance of defining and studying CFS 

population subgroups.

Cytokines are a problematic measure. They are descriptive, providing a helpful sense of what is occurring,

but difficult to measure reliably. Messenger RNA

upregulated for cytokines is a sensitive marker being

used by a number of researchers. Another widely

accepted method of measuring cytokines is to put

lymphocytes into a culture and stimulate them, and

then measure how much cytokine the lymphocytes

make in the maintenance of that culture. Some published data support using combinations of these

markers or methods to sort out the cytokine problem. TNF-α is one of the more interesting cytokines.

Cluster analyses have shown the pro-inflammatory

cytokine cluster in the type 2 cytokine pattern, plus

around TNF-α, which seemed to be a central core

cytokine in expression. Other research has found that

cross-sectional work was not useful when looking at

cytokines, because expression varies according to symptom severity, with the most severely affected patients

expressing cytokines most significantly. Following

patients longitudinally reveals a changing pattern, 

limiting cross-sectional study and highlighting the

need for care in designing models. Longitudinal design

should be a key component of any model study because the effects of duration and severity of illness 

at any given point can significantly affect markers.

24 Evaluating Immune Function in CFS
In one study, CFS patients were shifted from 

type 2 to type 1 cytokine expression. This was 

an elaborate study in which researchers extracted

lymph nodes, grew cells and forced them in vitro 

into type 1 patterns, then reinfused them into

patients, thus forcing the type 1 cytokine pattern

upon a patient. In six of the seven patients in 

whom this change was achieved, significant clinical improvement occurred in cognition, fatigue, 

and overall quality of life. This was an important 

observation, although it could be deemed an 

indirect consequence. A placebo-controlled trial 

is needed for the result to be considered reliable.

Studies of immune complexes circulating in 

antinuclear antibodies in CFS patients are also 

interesting but none have yet been conducted that 

take into account duration of illness. Whether 

long-term patients are making measurable autoantibodies or whether autoantibodies are mediating the illness in early onset patients is not 

known. This type of model suggests that duration should have an effect and that longer-term

patients would be more likely to express measurable autoantibodies.

A similar question considers whether allergy is 

a consequence or a cause. While there is general 

agreement that the cause of CFS is poorly understood, data suggest that some CFS patients have

measurable increased allergy expression; there 

are also some dissenting studies.

Natural killer (NK) cell data are more consistent 

and a large number of groups have described NK 

cell dysfunction in CFS populations; however, 

some researchers have failed to find that effect. 

This dichotomy points to the need for subgrouping—

NK cell dysfunction is a characteristic of one subgroup of patients who might be more likely than

others to respond to immunomodulatory approaches.

Ongoing work on the mechanisms of NK cell dysfunction is examining perforin content. CFS patients

have been found to have abnormally low levels of

perforin in NK cells compared to healthy controls,

but similar levels to patients with human immunodeficiency virus (HIV). Perforin may be a useful 

surrogate for NK cell function because it can be

frozen and thawed, whereas NK cells are not reliable

after thawing. Different methodological strategies 

are being examined to improve reliability across

research centers.

Longitudinal design should be a key

component of any model study because

the effects of duration and severity 

of illness at any given point can 

significantly affect markers.

Survivors of Hurricane Andrew, which devastated 

parts of south Florida in 1992, constitute the cohorts

for a number of studies. Initially the hurricane was

considered an acute stressor, but continuing hardships changed the storm into a chronic stress model.

Patients with low cognitive difficulties had much 

better immune function (measured by phytohemagglutinin T cell function in vitro), again indicating 

that cognitive difficulty seems to be a useful split 

line on cell function. In a CFS population, patients

with the lowest NK cell function had the most 

severe fatigue and the most severe cognitive difficulty, as measured by passive digit span tests and 

cognitive difficulty scores. However, patients with 

normal NK cell function had more depression.

Depression did not seem to be a mediator of the 

cognitive findings or severity of illness.4

T and B cell function in vitro were also measured;

these tests are tedious and expensive and not often 

done, but the predominant literature suggests abnormalities in T and B cell function. Only a few studies

have been conducted on delayed-type hypersensitivity (DTH) in CFS populations, but Lloyd’s group 

has shown that DTH is reduced in CFS patients. In an

ongoing prospective study of acute infectious illness 

by that group, it appears that reduced DTH predicts

long-term fatiguing illness after acute viral or bacterial illness.

In the review of the body of work in this field, a 

number of limitations became apparent. A problem

throughout the literature is population size, with 

most studies using low numbers that result in problematic statistical power. Problems are also apparent

in describing study populations and specifics of study

design. In all such studies, researchers need to thoroughly explain their methodologies. 

Since CFS is primarily a disease of women, time 

of hormonal cycles when blood samples are drawn

may be relevant and should be recorded. Circadian

rhythms are also relevant to immune function, 

particularly in the CFS population. Longitudinal

Evaluating Immune Function in CFS 25
relapse pattern is another factor that has not been

taken into account in many studies, and using longitudinal designs is critically important. Cross-sectional

studies are limited; they do not, for example, indicate

whether immune activation is a preceding or a coincidental event, follows the periods of exacerbation,

relates to symptoms, or explains the nature of the

autonomic and/or endocrine mediators.

Concerns about laboratory methodology are mentioned only rarely in the literature. Many samples 

are volatile and must be frozen quickly to yield a 

reliable measure. The reference laboratories must 

be competent. Some measures are not reliable after

shipping by typical overnight services because the

samples must be kept at certain temperatures.

Consistent measures and a consistent panel for 

measuring a highly volatile and interchangeable 

system should be established; a five-point panel 

may not be appropriate because there are not five

measures that adequately describe what is occurring

in CFS. A common protocol and commonalities in

goals for CFS researchers are needed. Reference 

populations vary and should be reviewed—while

study populations are usually women, often the 

normal controls are not gender matched. People

skilled in study design and analysis should become

involved in setting future directions for CFS research.

Multicentered longitudinal studies with well-described

populations and methodologies are needed. Before

studies are implemented, method and expertise of

research groups should be considered, so that groups

most suited to a specific project can become involved.

Proficiency standards must be established.

Discussion

Dr. Van Konynenberg: It is well supported that most

people with CFS have a history of some sort of stress,

and sometimes a combination of stressors over a 

long duration, and it is well supported that the body

responds to stress with the HPA axis. Assuming that

people with CFS are healthy until they become ill,

particularly acute onset patients, we can also assume

that the HPA axis was working normally until they

became ill. That means cortisol and epinephrine were

elevated, sometimes over long periods of time. Suppression of the immune system occurs, resulting in the

onset of conditions that TH-1 is supposed to defend

against, but TH-1 is not there to do so. At this point

in the pathogenesis, the depletion of glutathione

comes into play. At the last meeting of the American

Association for Chronic Fatigue Syndrome, a report

on a study showed glutathione depletion. Why is that

important and how does it happen? We know that

epinephrine is elevated. We know that a certain fraction of epinephrine oxidizes to form adrenochrome,

one of the oquinones that the body deals with using

glutathione. The Phase II detoxification for the

oquinones is glutathione conjugation, so there is a

mechanism to deplete glutathione from elevated epinephrine secretion over long times. Other things also

serve to deplete glutathione as well, including toxin.

So glutathione decreases and that also suppresses 

TH-1, and then comes the onset of the viral infection.

References

1. Patarca-Montero R, Antoni M, Fletcher MA,

Klimas N. Cytokine and other immunologic

markers in chronic fatigue syndrome and their

relationship to neuropsychological factors.

Applied Neuropsychiatry 2001;8:51-62.

2. Cruess SE, Klimas N, Antoni MH, Helder L,

Maher K, Keller R, Fletcher MA. Immunologic

status correlates with severity of physical symptoms and perceived illness burden in chronic

fatigue syndrome patients. J Chronic Fatigue

Syndrome 2000;7(1):39-52.

3. Antoni M, Cruess SE, Weiss D, Klimas N, Maher

K, Fletcher MA. Immune predictors of severity of

illness in CFS. Poster presentation, AACFS

International Conference on Chronic Fatigue

Syndrome, Fibromyalgia and Other Related

Illnesses (Biennial Research, Clinical, and Patient

Conference); 2003 Feb 1.

4. Lutgendorf SK, Antoni MH, Ironson G, Fletcher

MA, Penedo F, Baum A, Schneiderman N, Klimas

N. Physical symptoms of chronic fatigue syndrome are exacerbated by the stress of Hurricane

Andrew. Psychosom Med 1995 Jul-Aug;

57(4):310-323.

26 Evaluating Immune Function in CFS

Since CFS is primarily a disease of women, time of hormonal cycles 

when blood samples are drawn may be relevant and should be recorded.
Stress and Antidepressant Modulation of the Limbic HPA Axis 27

Chronic fatigue syndrome and depression are

comparable in many ways. It is important for

people who study CFS to know about depression and for people who study depression to know

about CFS. Traditional phenomenological categories

may no longer be relevant and the field may be dividing itself artificially. A great deal can be learned about

diseases by comparing their common aspects, such as

common symptoms. 

The HPA axis, the classic neuroendocrine system that

responds to stress, is not the only system that responds

to stress. The system is geared to making glucocorticoids (cortisol in humans and corticosterone in rats).

Both the peripheral organs and the brain are targets

for glucocorticoids. The HPA axis can be referred 

to as the limbic-hypothalamic-pituitary-adrenal axis,

because limbic components are an integral part of 

the system, particularly the hippocampus, which is 

an important area for memory and mood and a 

target for HPA activity.

HPA axis dysregulation exists in 

multiple diseases, including depression,

hyperactivity, and CFS.

The stress response is an adaptive response that,

under conditions of chronic demand, becomes maladaptive. HPA axis dysregulation exists in multiple

diseases, including depression, hyperactivity, and 

CFS. The paraventricular nucleus (PVN) of the 

hypothalamus, where corticotropin-releasing hormone (CRH) is produced, lies at the junction of 

multiple circuits and neurotransmitters, with many

different inputs. Regarding the acute effects of antidepressants, the monoamines and adrenaline and

serotonin have most of the input to the PVN. In 

general, monoamine release activates the system. 

An acute injection of monoamines in or peripheral 

to the hypothalamus will trigger an acute release of

CRH, ACTH (adrenocorticotropin), and cortisol. 

As a mechanism of antidepressants, particularly 

tricyclic antidepressants and serotonin reuptake

inhibitors, a monoamine neuron and norepinephrine are released into the synapse and then 

taken back by a transporter. Antidepressants 

block the uptake area, in effect allowing more

monoamines in the synapse.

This acute effect is necessary for antidepressant

action, but is not the only necessary step because 

antidepressants to treat mood disorders and other 

diseases do not work immediately; days, weeks, 

and sometimes antidepressant action is observed 

only after months. Current thinking is that chronic

modulation of some of the receptors is what underlies the antidepressant action. Blocking reuptake

acutely results in an increase in norepinephrine, 

and an acute antidepressant administration also 

causes an increase in ACTH.

Animal Studies

My laboratory examined the effect of antidepressants under baseline conditions. In one study, 

rodents were injected with imipramine, a tricyclic

antidepressant, and corticosterone was measured 

24 hours after each injection. After 3 days of injections, an enhancement of imipramine was seen in 

the synapse as was an increase in corticosterone,

although the findings were somewhat obscured 

by “noise.”

The HPA axis is geared to maintain optimal cortisol

levels and is difficult to dysregulate because this is

such an important function. The system seems normal before people become ill, but it may be working

hard to compensate to keep the cortisol level normal.

This compensation may be what ultimately causes 

the dysregulation. Researchers are beginning to look

at the effects of antidepressants and stress in the 

brain with the idea that, even though the cortisol 

Stress and Antidepressant Modulation of the Limbic HPA Axis

Juan F. López, M.D.
levels are normal, dysregulation is occurring at 

other sites such as the limbic brain and particularly

the hippocampus.

Two types of corticoid receptors exist in the brain: the

mineralocorticoid receptor (MR) and glucocorticoid

receptor (GR). They mediate the action of glucocorticoids in the brain and periphery. MR has a more 

limited distribution in the hippocampus and septal

regions than GR; GR has a wider distribution in 

the hippocampus, hypothalamus, and frontal cortex. 

MR and GR are also important because they control

the activity of the HPA axis: they signal the brain to

shut the system down under normal circumstances.

Classically, MR is high-affinity, low-capacity—it 

avidly takes on glucocorticoid but saturates easily—

whereas GR is low-affinity, high-capacity. 

With exposure to a stressor, MR becomes fully 

occupied, and GR takes over and then shuts the 

system down. Some scientists believe that MR is 

more important for circadian rhythm. MR and 

GR are important for both acute and chronic stress

because they are both occupied when the organism 

is stressed. It has been proposed that an MR/GR 

balance is essential for maintaining the tone of the

HPA axis; it is also essential for the homeostasis 

of the organism and how the organism responds 

to stress.

An altered MR/GR balance is a possibility in many 

of the diseases associated with stress, as noted by 

a number of researchers. We use a model of chronic

unpredictable stress (CUS) to study the GR antimargin expression and the effect of antidepressants.

In our study, rodents were stressed with different

stressors daily at different times of the day, so that 

the time and nature of the stressor was unpredictable. (Stressors included a swim, restraint, cold, 

noise, ether, and crowding.) Unpredictability adds

psychological stress to the physical stress. Rodents

have been found to be resilient to more predictable

stressors, which cease being a stressor as the animal

becomes accustomed to it. 

Some behavioral abnormalities are seen in this socalled animal model of depression (which is not a 

useful label because it is not possible to determine

whether a rat is experiencing mood problems).

Animals can help focus researchers on specific 

symptoms or behaviors that may be amenable 

to physiological studies, and research has shown 

that behavioral “abnormalities” are reversed by 

antidepressants. CUS produces HPA hyperactivity,

and similar receptor changes have been seen in 

postmortem tissue examinations of humans with

major depressive disorder.

In one study, rodents exposed to chronic unpredictable stress were treated with either desipramine, 

a tricyclic antidepressant that is also a potent 

norepinephrine uptake inhibitor; or with zimelidine, a selective serotonin reuptake inhibitor (SSRI).

The corticosterone levels were increased a small

amount by both drugs, and chronic stress caused 

an increase in baseline corticosterone. When desipramine was administered to the stressed animals, 

it blocked the stress-induced corticosterone increase,

but zimelidine did not have a similar blocking effect. 

It has been proposed that an MR/GR 

balance is essential for maintaining the

tone of the HPA axis; it is also essential

for the homeostasis of the organism and

how the organism responds to stress.

To understand the mechanisms at work, we 

examined MR and GR levels in the hippocampi 

of the sacrificed rats. CUS was seen to cause a 

downregulation of MR in the hippocampus, and

desipramine blocked downregulation but zimelidine did not. The antidepressant that was unable to 

block the stress response was also unable to block 

the downregulation. Sometimes downregulation is

seen with GR and sometimes it is not, depending 

on the nature of the stressor and the pressure and

strain on the rat. It can be difficult to decrease 

and easier to increase gene expression when the 

transcription rate of a gene is already low. Some

researchers have reported seeing downregulation 

of GR in the hippocampus.

The data suggest a link between peripheral corticosterone response or lack of it and MR regulation, 

but it is unknown whether MR downregulation 

is seen with chronic stress mediated by peripheral 

cortisol and how that can be tested. We performed

adrenalectomies on another group of stressed animals, hypothesizing that, if the adrenal is removed,

the corticosterone response would be gone because

the glucocorticoids would be absent. If it is a central response issue, the response should still be seen. 

One group of animals were adrenalectomized and

another adrenalectomized group was given cortisol 

28 Stress and Antidepressant Modulation of the Limbic HPA Axis
Stress and Antidepressant Modulation of the Limbic HPA Axis 29

in their drinking water, which helped maintain the 

circadian rhythm but eliminated the stress response.

We also looked for GR in the prefrontal cortex. 

The stressed animals showed an increase in baseline

corticosterone but within normal limits, but downregulation was seen in some of the subfields with

chronic stress. In general, eliminating the corticosterone response eliminated the MR downregulation

usually seen with chronic unpredictable stress. 

The GR also decreased in the stressed animals.

Another study tested and compared fluoxetine with

several different SSRIs. The animals were subjected 

to 28 days of chronic unpredictable stress. The control group in the study was an unhandled group, 

and a mildly stressed group was injected with saline.

Corticosterone increased slightly in the saline group.

Fluoxetine alone did not have an effect, but fluoxetine plus stress resulted in a significant increase in

corticosterone, a dramatic and unexpected finding.

Antidepressants clearly buffer the

effects of stress, which may have 

clinical applications to CFS.

One conclusion to be drawn is that antidepressants

have a different effect on a baseline organism than 

on an organism under stress. Fluoxetine blocked the

increase of corticosterone in the group injected with

saline (the mild stressor) but it did not block it in 

the CUS group; fluoxetine does not block the stress

response of a severe stressor that might be involved

with the epinephrine system. In the brain, there was

no difference in MR between the saline group and 

the unhandled group. However, even though fluoxetine did not block the corticosterone response, it did

seem to prevent the amygdala regulation: it seemed 

to protect the hippocampus from the effects of 

corticosterone, even though it did not block the 

corticosterone itself. This result was not observed 

in the frontal cortex. Downregulation of GR was 

seen in the frontal cortex and did not appear to 

be prevented by fluoxetine. 

Researchers are still trying to establish the meaning 

of these findings. Differential circuit effects have been

observed, an important consideration with antidepressants. Different antidepressants might have different

effects on the HPA axis, depending on what part of

the axis is examined. Chronic stress can modulate

glucocorticoid receptors, and this modulation, at 

least the downregulation, seems to be mediated 

by a group of corticoids.

Antidepressants clearly buffer the effects of stress,

which may have clinical applications to CFS. Failure of an antidepressant to block or modify the 

stress response is associated with failure of that 

antidepressant to correct the corticosteroid receptor

changes. In this particular animal model, tricyclic

antidepressants may be more effective than SSRIs 

in preventing these stress-induced corticosteroid

receptor changes.

Human Studies

Downregulation of the mineralcorticoid receptor 

is seen in unmedicated patients with a history of

depression and suicide. Even though MR is only

found in the hippocampus in rodents, it is found 

in the cortex of humans and probably plays a 

wider role in humans than in rodents. This is a

reminder that some animal findings apply to 

humans and some do not.

Serotonin is implicated in multiple functions, 

including mood, pain perception, sleep, and appetite. Part of the reason these multiple functions 

are possible is that serotonin projects to many 

different brain areas, such as the thalamus, the 

hippocampus, and the amygdala. There are multiple serotonin receptors; by 1993, 14 serotonin 

receptors were known, which gives serotonin 

many ways to modulate multiple functions. 

Most aspects of depression seem to be related 

to the 2A and 2C receptors; both are altered in 

suicide and depression, and both are known to

change with antidepressant treatment.

In the human hippocampus, the glucorticoid 

receptor is found on MR receptors, indicating 

that they must “talk” to each other. Researchers 

have seen downregulation of MR in the hippocampi 

of patients with mood disorders in postmortem 

studies. Several studies show downregulation in 

multiple areas of the brain. Other findings include

decreased receptor number and mRNA levels of 

the serotonin 1A receptor subtype (5-HT1a) in 

the rat hippocampus and prevention of the 5-HT

receptor changes with antidepressants. The serotonin 2A receptor has been shown to be increased 

in the prefrontal cortex of suicide victims suffering severe depression, and many antidepressants 

downregulate serotonin receptor binding.
Conclusions

Serotonin and the HPA axis are related in a variety 

of ways. Serotonin can increase release of CRH 

but, more importantly, serotonin receptors are colocalized with glucocorticoid receptors in the brain,

especially in the hippocampus. Many researchers 

have shown that glucocorticoids can modulate 

serotonin receptors. In the case of adrenalectomy, 

significant regulation of 1A in the hippocampus 

is seen, but some resupply of corticosterone normalizes this regulation. The receptor is more sensitive 

to glucocorticoids. What happens when an animal 

is chronically stressed? Antidepressants have different actions in stressed and nonstressed organisms. 

An example is what happens with the 1A receptor—

there is a downregulation of 1A with chronic stress,

but antidepressants prevent this downregulation.

Stress also causes change in the serotonin 2A receptor: the glucocorticoids upregulate 2A receptors

(important for mood and sleep) in the same direction as seen in depression. Antidepressants that 

block the corticosterone response prevent that 

upregulation. But fluoxetine or zimelidine (the 

SSRIs) do not block the corticosterone response 

or the 2A upregulation. Failure to block the stress

response is associated with a failure to correct 

the 5-HT receptor changes. In the animal models

studied, tricyclic antidepressants were more effective

than SSRIs in preventing stress-induced 5-HT 

receptor changes, at least with severe chronic stress.

Applications to CFS

Our research found GR and MR dysregulation in

postmortem tissue of patients with mood disorders

and wondered if the same downregulation would 

be seen in CFS patients. Researchers should conceptualize CFS as a brain disease and correlate clinical

observations with brain studies, including in vivo 

PET scanning and brain collections as used in the

study of mood disorders. Brain collections provide 

an opportunity to examine mRNA and conduct

detailed cellular studies.

It is clear that the HPA axis dysregulation itself 

can cause or worsen serotonin receptor abnormalities in some CFS patients. Glucocorticoids 

can directly affect serotonin receptor levels, which

suggests a means to regulate the receptors in the 

case of serotonin function problems. Glucocorticoids

and many other hormones (for example, estrogen)

modulate serotonin receptors. Correcting the HPA

axis dysregulation may be necessary for a treatment

response to occur; patients with uncorrected HPA 

are more likely to relapse after treatment with 

antidepressants. 

Regarding the differential effects of medication in 

the HPA axis, the goal in a hypocortisolemic state 

is to increase cortisol levels; one suggested technique

is to use positive stress such as exercise. Some data

suggest that people with atypical depression have 

low cortisol levels, and SSRIs are more effective 

for atypical depression than are tricyclic antidepressants. There is an optimal level of glucocorticoids 

for good brain function: too much or not enough 

can have important implications for how many 

systems work.

In one study, patients with CFS receiving lowdose dexamethasone (synthetic cortisol) showed

hypersensitivity to feedback.1 This raises the 

question of whether the brain will perceive the

enhanced sensitivity as increased cortisol, even 

though the levels are low. A differential sensitivity

may be important; multiple systems are involved 

with CFS, and it is necessary to understand how 

they interact.

There is an optimal level of 

glucocorticoids for good brain 

function: too much or not enough 

can have important implications 

for how many systems work.

Discussion

Dr. Van Konynenberg: A paper by Logan 2 years 

ago indicated that in CFS, serotonergic activity is 

elevated, and a recent paper by the Glasgow Group

showed high tryptophan and low tyrosine in the

blood of CFS patients. Tryptophan is the precursor of serotonin and tyrosine is the precursor of

dopamine, so they are arguing that serotonergic 

activity is high and dopaminergic activity is low.

Dr. Ottenweller: In our work at New Jersey 

Medical School, researchers have been trying to 

connect stress and CFS. Your stress models of the 

animals show hypocortisolemia, predicting low 

levels of cortisol for humans. We do not see low 

levels of corticosterone in any animal stress model

and our group has worked with half a dozen.

30 Stress and Antidepressant Modulation of the Limbic HPA Axis
Stress and Antidepressant Modulation of the Limbic HPA Axis 31

Dr. López: Not all stress works equally, which 

is why we went to chronic unpredictable stress. 

We do not always see big changes. It has to do 

with the nature of the stressor. Also, some people

adapt to stress. As I said earlier, the system is 

tightly regulated to maintain normal levels.

Sometimes it must be pushed to see differences.

Some of the rodent work dealing with antidepressants and early life stress might have some 

applicability to CFS. When a pup is stressed 

and with the mother, there is little corticosterone

response; but when the mother is removed, there 

is a large response. When pups were injected with

desipramine, the response matured so that five 

of the animals not responding to corticosterone

responded, even with their mother. Sometimes 

antidepressants may be effective in bringing a 

system back to normal. 

Stressors are different; stress is not depression 

and stress is not chronic fatigue. These things 

are predisposing. If the body has a weak link, 

a stressor will take advantage of it. Early life 

stressors have been implicated in medical illnesses, depression, and CFS, almost at a 

comparable level to genetic vulnerability.

Reference

1. Gaab J, Huster D, Peisen R, Engert V, Schad T,

Schurmeyer TH, Ehlert U. Low-dose dexamethasone suppression test in chronic fatigue syndrome

and health. Psychosom Med 2002;64:311-318.

HPA Axis and Autonomic Nervous System Function in Fibromyalgia 33

An internal biological clock has an important

influence on the 24-hour biological rhythms

for hormone levels (adrenocorticotropic hormone [ACTH], cortisol, melatonin, and growth hormone), sleepiness and wakefulness, subjective mood,

objective performance, and core body temperature.

Misalignment of the endogenous circadian rhythm

with the sleep/wake cycle causes disturbed sleep at the

desired sleep time, fatigue and problems in remaining

awake during the day, impaired cognitive function,

gastrointestinal upset, and inappropriate timing of

hormone release. Misalignment is sometimes seen 

in individuals experiencing jet lag or engaging in 

shift work, and in some people who are blind. 

A procedure called the “constant routine” can be

used in humans to help identify internal circadian

rhythms. The constant routine consists of 40 hours 

of uninterrupted wakefulness, with constant posture,

hourly small meals, controlled activity, and low light

levels to measure melatonin, which is suppressed by

light. The goal of the constant routine is to carefully

control the environment in order to uncover an

endogenous biological rhythm. For example, during a normal 24-hour day with a normal sleep/wake

cycle, a person’s core body temperature dips during

sleep; however, it is not clear whether that dip is related to sleep or to an endogenous circadian rhythm. In

the constant routine, a dip in core body temperature

is seen during the habitual sleep period indicating a

circadian rhythm in core body temperature. Sleep

intensifies the dip in core body temperature, showing that both sleep and the internal biological clock

influence core body temperature. 

The symptoms associated with circadian misalignment occur in patients with fibromyalgia and chronic

fatigue syndrome, raising the question of whether 

circadian rhythm misalignment could be occurring 

in patients with these conditions. Dr. Adler and colleagues designed a study protocol to address this

question in fibromyalgia patients.1 The subjects 

were premenopausal women who were not taking 

any medications (including any type of steroid, even 

if applied topically or taken only transiently) during

the past year and who were not depressed. The nosteroid requirement eliminated almost 30 percent of

the group’s fibromyalgia patients and 10 to 20 percent of the healthy controls. All subjects were studied

in the follicular phase of the menstrual cycle. For 3

weeks before the study, to establish baselines, the 

subjects kept a sleep/wake log and followed their 

normal sleep/wake cycle, which they were asked 

to keep regular. A total of 15 fibromyalgia patients

and 14 controls were studied.

After the 3-week period, the subjects were admitted

to the hospital and their sleep was monitored 3 nights

in a row. The first night was considered a night of

acclimation, when subjects often do not sleep well.

The second night was a night of recovery sleep. The

third night’s sleep, which was lying flat in the dark,

was considered a better reflection of normal sleep.

The constant routine began when the subjects awakened after the third night. The head of the bed was

raised to 30 degrees and the lights were adjusted 

to a very low level, 10 lux. Every 20 minutes the 

subjects filled out a computerized questionnaire 

asking if they felt alert or sleepy. A normal circadian

rhythm in sleepiness and wakefulness was seen in

both control and fibromyalgia subjects. Stiffness 

and pain were also measured and no association 

with circadian rhythm was noted, although fibromyalgia patients complained of more stiffness and

pain than did the controls. Analysis of melatonin, 

cortisol, and core body temperature found no differences between the subjects and controls. Thus,

individuals with fibromyalgia show no evidence 

of circadian rhythm misalignment. Furthermore, 

cortisol and melatonin levels did not differ between 

the control and fibromyalgia subjects. 

HPA Axis and Autonomic Nervous System Function 

in Fibromyalgia

Gail Kurr Adler, M.D., Ph.D. 
In a subset of control and fibromyalgia subjects, heart

rate was studied during the sleep period and the following 40-hour constant routine. While the controls

had the expected slower heart rate during the sleep

period, the fibromyalgia patients did not. Examining

high frequency and low frequency as a percentage 

of total power through spectroanalysis of heart rate

revealed some shifts between sleep time and constant

routine. For each of these parameters, mean values

were calculated for the 8-hour sleep time and the 8-

hour habitual sleep time during the constant routine.

The results showed differences in autonomic control

of heart rate between the two time periods in the different subject groups. However, no differences were

found in total sleep time, or amount of time spent in

rapid-eye-movement sleep or stages 1, 2, 3, or 4 of

sleep. These findings suggest significant differences 

in heart rate and heart rate variability during sleep

between subjects with fibromyalgia and healthy controls, differences not due to sleep architecture or alterations in circadian phase. Patients with fibromyalgia

may have decreased parasympathetic and increased

sympathetic nervous system modulation of the sinus

node compared to healthy women.

In another study, autonomic function was examined

with the application of the stimulus of low blood

sugar.2 This was done using a hypoglycemic, hyperinsulinemic clamp and a constant insulin infusion,

with serum glucose measured every 5 minutes. The

rate of glucose infusion was adjusted to maintain 

the patient’s glucose at a set level. Glucose was kept

at a normal level (90 mg/dl) for 30 minutes, then

dropped every 30 minutes, down to 40 mg/dl, providing a precise, quantifiable, exogenously controlled

hypoglycemic condition that was not affected by the

subject’s endogenous hormone release. Hypoglycemia

stimulated a rise in plasma epinephrine in healthy

controls. This increase in epinephrine was approximately 30 percent lower in the fibromyalgia patients.

In a provocative related finding, the Fibromyalgia

Impact Questionnaire was used to obtain an overall

assessment of activities of daily living, and patients

with the worst health status had the lowest epinephrine response to hypoglycemia.

Hypoglycemia is also known to turn on the HPA 

axis, and this response was studied in the same group

of patients. When patients are treated with cortisol, 

it feeds back and turns off CRH and ACTH; when

treatment ceases, the HPA axis is suppressed and

patients may experience symptoms of steroid withdrawal, including fatigue, malaise, muscle aches, 

sleep disturbances, gastrointestinal complaints, 

difficulty thinking, dizziness upon standing, fever, 

and nausea—all complaints seen in CFS and fibromyalgia patients. Researchers in this study were 

looking for HPA axis disturbances in fibromyalgia

patients. ACTH rose in response to hypoglycemia 

in fibromyalgia patients, but to a lower level than 

in controls. Similar prolactin responses to hypoglycemia were observed in control and fibromyalgia

subjects. Possible explanations for the reduced ACTH

response could be a defect in signals coming from the

hypothalamus or a defect at the level of the pituitary.

Three of four published studies report a significantly

increased ACTH response to an infusion of the hypothalamic secretagogue CRH, while one reports a 

normal-to-increased response.3-6 These studies argue

against a primary defect at the level of the pituitary

and may indicate a problem in hypothalamic function. The elevated ACTH response could result from

chronically low CRH levels, leading to upregulation

of CRH receptors on the pituitary and producing an

exaggerated response when CRH is administered.

These findings suggest significant 

differences in heart rate and heart 

rate variability during sleep between

subjects with fibromyalgia and 

healthy controls, differences not 

due to sleep architecture or 

alterations in circadian phase.

The cortisol responses to hypoglycemia were similar in control and fibromyalgia subjects. In addition,

ACTH dose response curves performed with infused

ACTH showed a normal cortisol response in fibromyalgia patients. Infusions with angiotensin II in 

a dose response fashion in patients with a low salt

balance also showed a normal aldosterone response.

Thus, the adrenal responds normally to both cortisol

and aldosterone secretagogues.

In seeking an explanation of the changes in ACTH

and epinephrine seen in the above studies, researchers looked for a way to link the HPA axis and autonomic nervous system. A body of data from animal

and human studies suggests important interactions

between the two systems. A series of studies performed by Davis and colleagues have examined the

effect of an antecedent stress on the autonomic and

hormonal response to subsequent hypoglycemia in

healthy humans.7 The subjects underwent a series 

34 HPA Axis and Autonomic Nervous System Function in Fibromyalgia
HPA Axis and Autonomic Nervous System Function in Fibromyalgia 35

of 2-day studies separated in time. On day 1, the 

subjects received either a stress or a placebo stress

and on day 2 the hormonal and autonomic nervous

system responses to hypoglycemia were assessed.

Subjects who, on day 1, experienced prolonged hypoglycemia or very vigorous exercise showed reduced

hormonal and autonomic responses to the day 2

hypoglycemic stress; specifically, reductions in the

ACTH, autonomic nervous system, growth hormone,

beta-endorphin, and pancreatic polypeptide responses

to hypoglycemia. Day 1 hypoglycemia also reduced

the hormonal and autonomic responses to day 2 exercise, indicating that antecedent stress can blunt the

responses to a variety of stressors. Subjects who, on

day 1, received an infusion of cortisol designed to

raise circulating cortisol levels to those observed during

stress also had markedly reduced hormonal and autonomic response to day 2 hypoglycemia. One resulting hypothesis is that stress-induced rises in cortisol,

through inhibition of CRH, inhibits the ACTH, hormonal, and autonomic responses to subsequent stress.

These results suggest a link between the HPA axis and

the autonomic nervous system in their responses to

stressors. This finding has important implications for

hypoglycemia-associated autonomic failure, a syndrome

of hypoglycemic unawareness in insulin-dependent

diabetes patients who have frequent hypoglycemic

episodes and lose their ability to perceive the symptoms of hypoglycemia, without the usual response 

of increased epinephrine or cortisol. In these patients

profound and prolonged hypoglycemia can lead to

coma and death. When blood glucose is controlled

and the stress of hypoglycemia is carefully avoided,

the hormonal and autonomic nervous system 

responses improve over several weeks.

A working model for the pathophysiology of fibromyalgia should include genetic factors, gender effects,

environmental factors, and use of steroids or other

drugs, all of which can be implicated in the decrease

in CRH or autonomic function (see Figure 1). Because

of the feedback between these two systems, a defect

in one may lead to a defect in another. Many animal

studies suggest that both the autonomic nervous system and CRH can influence pain perception, which

may explain the increased sensitivity to pain in fibromyalgia patients. Both of these systems influence

sleep, gastrointestinal function, cognitive function,

blood pressure, and hormone levels.

In fibromyalgia patients, a therapeutic goal might be

to increase the dynamic range of the normal rhythms

in HPA axis and autonomic function, so that when a

stress occurs, the systems are turned on and are also

capable of being turned off appropriately. If these two

systems are suppressed, attention should be given to

ways in which their activities can be increased. 

These results suggest a link between the

HPA axis and the autonomic nervous

system in their responses to stressors.

Figure 1. A working model for the pathophysiology of fibromyalgia.
References

1. Klerman EB, Goldenberg DL, Brown EN,

Maleszewski AM, Adler GK. Circadian rhythms

in women with fibromyalgia. J Clin Endocrinol

Metab 2001;86(3):1034-9.

2. Adler GK, Kinsley BT, Hurwitz S, Mossey CJ,

Goldenberg DL. Reduced hypothalamic-pituitary

and sympathoadrenal responses to hypoglycemia

in women with fibromyalgia syndrome. Amer J

Med 1999;106:534-543.

3. Crofford LJ, Pillemer SR, Kalogeras KT, et al.

Hypothalamic-pituitary-adrenal axis perturbations in patients with fibromyalgia. Arthritis

Rheum 1994;37:1583-92.

4. Griep EN, Boersma JW, de Kloet ER. Altered

reactivity of the hypothalamic-pituitary-adrenal

axis in the primary fibromyalgia syndrome. J

Rheumatol 1993;20:469-74.

5. Griep EN, Boersma JW, Lentjes EG, et al.

Function of the hypothalamic-pituitary-adrenal

axis in patients with fibromyalgia and low back

pain. J Rheumatol 1998;25:1374-81.

6. Riedel W, Layka H, Neeck G. Secretory pattern

of GH, TSH, thyroid hormones, ACTH, cortisol,

FSH, and LH in patients with fibromyalgia syndrome following systemic injection of relevant

hypothalamic-releasing hormones. Z Rheumatol

1998; 57 Suppl 2:81-7.

7. Davis SN, Shavers C, Costa F, et al. Role of cortisol in the pathogenesis of deficient counterregulation after antecedent hypoglycemia in normal

humans. J Clin Invest 1996;98:680-91.

36 HPA Axis and Autonomic Nervous System Function in Fibromyalgia
The Autonomic Nervous System 37

Amajor theme of chronic fatigue syndrome

research (and psychosomatic research in 

general) is that stress regulates the inner 

world by way of the autonomic nervous system. 

The brain interacts with the external environment—

the outer world—by way of the central nervous 

system and its effects on skeletal muscle. The autonomic nervous system regulates the inner world 

by way of effects on smooth muscle, glands, and 

the cardiovascular system.

“Autonomic nervous system” was coined by Langley

almost a century ago. He was referring to the chain 

of ganglia lined up, like pearls on a necklace, outside

each side of the spinal column. These ganglia contain

nerve cell bodies and they lie outside the central nervous system. Langley thought they might have different

functions that were independent of the central nervous system; they were autonomous, so they were

“autonomic.” This view is incorrect, but the phrase

“autonomic nervous system” is still used. Langley’s

autonomic nervous system had three components: 

an enteric nervous system; a gastrointestinal tract, of

which the neurotransmitters are unknown and the

multiple possible functions poorly understood; and

the parasympathetic nervous system, which opposes

the sympathetic nervous system.

The autonomic nervous system 

regulates the inner world by way of

effects on smooth muscle, glands,

and the cardiovascular system.

The “sympathetic nervous system” is an ancient

phrase that goes back to the time of Galen, whose

ideas dominated medical thought from the second

century until Harvey’s description of the circulation 

of the blood in 1648. Galen taught that there are 

spirits in the body: animal spirits, vital spirits, and

natural spirits. The animal spirits were distributed 

by the nerves, which were conduits by which the 

animal spirits would coordinate functions of the

body’s organs. These spirits worked in concert with

one another, in “sympathy” with one another. The

phrase “sympathetic nervous system” antedates the

idea of the circulation of the blood by 14 centuries,

and no one has produced strong evidence for the 

existence of the spirits. However, the idea that the

sympathetic nervous system plays an important role

in coordinating body functions is essentially correct.

In the early twentieth century, Walter Cannon, 

the American physiologist who coined the phrase

“fight-or-flight” and the word “homeostasis,” introduced another component to the autonomic nervous

system: the adrenal medulla. Cannon taught that 

the sympathetic nervous system and adrenomedullary systems were a functional unit, which became 

known as the sympathoadrenal system, the sympathoadrenomedullary system, or the sympathicoadrenal

system. This system is an emergency system, not 

necessary for daily activities, that is required for 

fight-or-flight emergencies. Cannon was so convinced

about this unitary sympathoadrenal system that, in

the mid-1930s, he formally proposed that the hormone released from the adrenal medulla (adrenaline)

also was the chemical messenger of the sympathetic

nerves. He was wrong, and this cost him a Nobel

Prize because, in 1946, Von Euler correctly identified

the sympathetic neurotransmitter as norepinephrine

—adrenaline’s “father” in the catecholamine family,

which is closely related but not identical—and Von

Euler shared a Nobel Prize for that discovery in 

1970. The idea of a unitary sympathoadrenal 

system has persisted to this day. Evidence indicates

not only that these are separate components of the

autonomic nervous system but also that they are 

separately dysregulated in at least one condition 

that is associated with chronic fatigue.

Session Two: The Autonomic Nervous System

Chair: David Goldstein, M.D., Ph.D.
A fifth component to the autonomic nervous system

deals with sweat—sweating in response to a gustatory

stimulus such as eating chili peppers, to emotional

stress, and for thermoregulation. Sweating is a sympathetic function that is mediated by acetylcholine as 

its transmitter. A person who has chronic fatigue,

defined as orthostatic intolerance and orthostatic

hypotension from a problem with the ability to 

synthesize norepinephrine, should be able to sweat

normally. Patients who have CFS often have orthostatic intolerance. 

In 1946,Von Euler correctly 

identified the sympathetic neurotransmitter as norepinephrine.

Two forms of chronic orthostatic intolerance are 

associated with CFS, and patients often have different

results in the positive tilt table test. In one result, the

patient faints, having developed neurally mediated

hypotension and a sudden drop in blood pressure,

usually with a relative or absolute bradycardia, which

is what constitutes the positive tilt table test. Other

patients, or sometimes the same patients, can have 

an excessive increase in pulse rate and postural tachycardia, with or without subsequent fainting. In one

study, regardless of a type of response or whether it

was both, the tilt table test was considered positive.

Approximately 60 percent of the patients tested 

with CFS had a positive tilt table test, indicating 

that orthostatic intolerance, as indicated by the

responses to tilt, is common in CFS.

Fainting is associated with two classic features, which

indicates the absence of a unitary sympathoadrenal

system. The first is a failure of the sympathetic nervous system. Multiple studies have used multiple 

measures of sympathetic outflow, including direct

sympathetic nerve recording showing that a loss 

of sympathetic outflow, at least within the skeletal

muscle and heart, is characteristic of neurocardiogenic syncope (the sympathetic withdrawal). At 

the same time, everybody knows that people who

faint turn pale, which is cutaneous vasoconstriction.

Sympathetic withdrawal does not cause cutaneous

vasoconstriction. Adrenaline and epinephrine are

major culprits—these patients have high adrenaline

levels, which is why they are pale. How can high

adrenaline levels and withdrawal of sympathetic 

outflow occur at the same time with only a 

unitary sympathoadrenal system?

Most but not all patients in a tilt-testing study

referred for tilt table testing because of orthostatic

intolerance also had a complaint of chronic fatigue.

Normally, forearm vascular resistance goes up; in this

study, the forearm vascular resistance approximately

doubled. Norepinephrine doubled or tripled, which 

is also normal. Adrenaline or epinephrine goes up 

by the same proportion, so that the increase in 

norepinephrine as a fraction of baseline, divided 

by the increase in epinephrine as a fraction of 

baseline yields a value of approximately 1.

In a patient with neurocardiogenic syncope tilted, 

at first the forearm vascular resistance goes up as 

it is supposed to, but then gradually it creeps down

and eventually falls below 1. The forearm is now

vasodilated compared to baseline and, within minutes, the patient has had syncope. Norepinephrine

and epinephrine both go up normally by the same

proportion. As the tilt goes on, norepinephrine

increases a little and epinephrine goes up progressively. As a mirror image to the forearm vascular

resistance, sympathoadrenal imbalance occurs and

adrenaline goes up more than norepinephrine.

To understand the mechanism of syncope, it is necessary to understand what causes sympathoadrenal

imbalance and what causes forearm vasodilation,

because these events occur before hypotension. 

In this study, the people who had neurocardiogenic

syncope, on average, showed sympathoadrenal imbalance of more than ten times normal. After the 

syncope, sympathoadrenal imbalance remains and,

with recovery, elevated epinephrine persists and 

helps explain why people feel sick after a positive 

tilt table test, often for hours or even days.

Between episodes, it is not yet clear whether any

abnormalities occur in people who faint a lot, either

with postural orthostatic tachycardia syndrome

(POTS) or without. Many patients who faint say 

they do not feel right: “I have fatigue,” “I can’t 

get up,” “I can’t tolerate heat,” “I can’t eat a large

meal,” “I feel disabled,” “I can’t exercise because I

feel terrible afterwards,” or “We have this JacuzziTM

and I don’t know what to do with it.” This predisposition is caused by a failure of the sympathetic

nervous system. In a study on sympathoadrenal

imbalance, two groups of patients, one with POTS

and the other with syncope, differed remarkably 

in cardiac sympathetic function. This function is

assessed by infusing tritiated norepinephrine. To 

figure out how much norepinephrine is entering 

38 The Autonomic Nervous System
The Autonomic Nervous System 39

the venous blood of the heart, it is necessary to 

figure out the extent of dilution of the radioactive

norepinephrine as it goes through. The results in

patients with chronic orthostatic intolerance showed

that, in POTS patients, the cardiac norepinephrine

spillover is high; in syncope patients, the cardiac 

norepinephrine spillover is low. This strong finding 

is independent of a cardiac event.

The first take-home lesson is that there is no sympathoadrenal system, because it is not a unitary system.

These systems are dysregulated independently.

Hans Selye, who introduced stress as a medical scientific idea, defines stress as a nonspecific response of

the body to any demand upon it. Because of that 

definition, the view arose that it does not matter 

what the stressor is—that giving IL-6 to someone is

the same as making someone hypoglycemic. Exercise

is an insolent stress and standing up and talking in

public is a stress; all stress is the same and a single

neuroendocrine stress response occurs and can be

studied. Whatever the stressor, the same syndrome

occurs and is characterized by adrenal enlargement

that translates into activation of the HPA axis, gastrointestinal bleeding, and suppression of immunity.

Every stressor has specific and nonspecific components. Selye was only interested in the nonspecific

response, that is, a common feature that was 

shared among all types of stress.

The concept of allostatic load can go 

a long way to introducing ideas about

how chronic stress or stressors can 

lead to long-term system breakdown.

Chrousos and Gold at the National Institute of

Mental Health (NIMH) and the National Institute 

of Child Health and Human Development (NICHD)

modified Selye’s theory importantly by introducing

the notion of a threshold. Stress or the stress response—

the stress syndrome—will be turned on if the intensity

of any stressor goes above a certain threshold. That

theory can be shown mathematically to be incorrect

because it does not account for the data. Pecak 

published a study in the American Journal of

Physiology in 1998 that tested and refuted the 

doctrine of nonspecificity.

What about a homeostatic definition of stress? 

A homeostatic system is like a house’s thermostat 

system. Afferent information is compared with set

points for responding, and the discrepancy is what

drives the multiple effectors, leading to relative

preservation of levels of the monitored variable. 

Stress is a condition, a state; in psychology, stress

would be called an intervening variable, analogous 

to an emotional or motivational state. Selye and 

his students only dealt with the HPA axis. Cannon

only dealt with the adrenomedullary model system.

Experts in any one of these systems maintain a view

that focuses on only one system.

Adrenaline plays a major role in distress. The

response to hypoglycemia involves stimulation 

of the adrenomedullary hormonal system, much 

more than the HPA axis. Water deprivation is 

stimulated by vasopressins, the body’s main waterretaining hormone. Salt deprivation is stimulated 

by the renin-angiotensin system; aldosterone is 

the body’s main salt-retaining steroid.

Fight is not the same as flight. A person who is 

terrified cannot make spit because spitting requires

intact sympathetic and parasympathetic nervous 

systems. Spitting is more than making saliva; it 

has an instinctively communicated signal value. 

Fight, flight, fright, and faint are different from 

one another and have different patterns, and one

dependent measure cannot show all these patterns.

Stellar introduced the term “allostasis.” To understand allostasis, think about the temperature and

humidity in a house. The goal of homeostatic systems is to keep all variables the same. In allostasis,

the settings are regulated dynamically and there is 

no ideal value for glucose, blood pressure, sodium, 

or temperature. A good example is a house in which

the windows have been left open for a year. There 

is no temperature regulation in that house, and the

systems have broken down; to keep the same allostatic setting requires use of the effector systems to

such an extent that they have failed. According to

McEwen, allostatic load refers to the long-term 

energy use or system use and damage because of 

wear and tear that results from some other factor

imposed on the system. The concept of allostatic 

load can go a long way to introducing ideas about

how chronic stress or stressors can lead to longterm system breakdown.

How can the sympathetic innervation of the heart 

be assessed? Sympathetic imaging agents can be 

used, the best studied of which is 123 I-MIBG 

(meta-iodobenzylguanidine). More than 600 studies 
of 123 I-MIBG have been conducted in the heart to

look at sympathetic innervation and function in a 

variety of diseases. Not a single study has come from

the United States (all were conducted in Europe and

Japan) because, until recently, 123 I-MIBG was not

available here.

A sympathetic imaging agent called fluorodopamine

was developed by Dr. Goldstein at the NIH. Fluorodopamine is a catecholamine—dopamine with a

positron-emitting isotope of fluorine at the sixth 

position on the benzine ring. Fluorodopamine works

as a sympathetic imaging agent and is removed rapidly from the bloodstream, as are all catecholamines.

Fluorodopamine in the interstitial fluid is taken up by

a process called Uptake One, which was discovered

by Julius Axelrod at the NIMH (who shared the

Nobel Prize with Von Euler in 1970). The radioactivity is translocated into vesicles in the sympathetic

nerve, allowing a view of the sympathetic nerves 

that are distributed homogeneously in the heart. 

In pure autonomic failure, the heart is not visible 

at all on such scans.

Shy-Drager Syndrome, or multiple system atrophy

with sympathetic failure, is associated with orthostatic hypotension and normal plasma and norepinephrine levels; innervation is present. The problem 

is with regulation of that innervation by the brain. 

In contrast, in patients with Parkinson’s disease and

orthostatic hypotension, there is a loss of sympathetic

nerves in the heart, demonstrating that Parkinson’s 

is not merely a brain disease and not merely a 

disease of the nigrostriatal dopamine system; it is 

also a disease of the sympathetic nervous system.

One way to get at function is by ligand displacement. If a lot of dopamine is being released from a

particular terminal, an easily displaced ligand could

be injected for the dopamine receptor. A drug, such 

as amphetamine, that increases extracellular fluid 

levels of dopamine could then be administered. 

The endogenous dopamine will compete with the 

ligand for the receptor and, if the conditions are 

right, a break in the line for radioactivity will occur 

if dopamine is being released. The ligand will be 

displaced; the radioactivity will come out.

This experiment has already been conducted for

Raclopride, looking at dopamine in the brain. It 

could also be done for parasympathetic cholinergic

innervation of the heart, because most of the receptors are muscarinic M2 receptors. If a loss of parasympathetic cholinergic terminals were to occur, as 

is posited from the heart rate variability approach 

in CFS, then prevention of the breakdown of endogenous acetylcholine by administering a cholinesterase

inhibitor would lead to a break in the curve if acetylcholine were present. If acetylcholine were not 

present to release, then no change in the binding

would be seen.

Ligand displacement is an alternative idea for looking at sympathetic and parasympathetic innervation

of the heart, as well as general neurotransmitter 

systems anywhere in the body.

40 The Autonomic Nervous System

Ligand displacement is an alternative idea for looking at 

sympathetic and parasympathetic innervation of the heart,

as well as general neurotransmitter systems anywhere 

in the body.
CNS and ANS Responses to Exercise in Patients with CFS 41

Many patients with chronic fatigue syndrome

say they do not feel too bad until they start

doing something, and that exercise is the

worst thing they can do. The most ideal stimulation

test to use in CFS is exercise because exercise exacerbates the illness. One of the most robust findings in

the field of CFS is that people with CFS do not like 

to exercise to exhaustion, probably because they 

find the effort of exercising much more difficult 

than when they were in good health.

Exercise, Perception, and CFS

Exercise scientists have used the rating of perceived

exertion (RPE) to measure the perception of effort

used to exercise. This scale runs from a value of 6

(very, very light) to 20 (very, very hard), and was

designed by Gunnar Borg of Sweden. Multiplying

each scale value by 10 produces an equivalent heart

rate value of 60 to 200.

Many studies show a close correlation between the

RPE during exercise and actual physiological effort.

In a study by Paul and colleagues, participants were

asked to exercise at only 40 percent of their maximum capacity. CFS patients had a much higher RPE

compared to the controls, perceiving more effort even

at the beginning. Edwards and colleagues compared 

a larger group of CFS patients with healthy controls.

When RPE (y axis) was graphed against heart rate 

(x axis), the linear curve shifted to the left for the

patients, consistent with greater effort perceived with

the same amount of physiological work. This result

occurs in all exercise studies with CFS and is probably the most robust finding in all CFS research.

We also know that this abnormality responds to

appropriate treatment. Fulcher and White administered graded exercise therapy (GET) for 12 weeks 

to 66 CFS patients who did not have a comorbid psychiatric disorder. Exposure to GET shifted the RPE

curve back to the right. Although GET participants

experienced increased fitness and increased strength,

these were not associated with getting better overall.

It appears that mere exposure to graded exercise is

what normalizes RPE and therefore GET is more a

“brain treatment” than a physical training treatment.

Apart from fitness and strength, research has shown

that several brain-mediated elements help determine 

a greater sense of effort with exercise:

• Sleep. Individuals who have trouble sleeping.

• Mood. People who are anxious or depressed.

• Somatic perceptions (introspections). People 

who are more aware of their bodies.

• Introversion. Those individuals who are 

more internally oriented.

• Emotionality. Individuals who generally 

react emotionally to events. 

In a 1990 study by Riley and colleagues, participants

with CFS were asked to estimate how fit and well

they were before they developed CFS. They were

compared with people who were currently healthy

and with people who had irritable bowel syndrome.

People with CFS reported that their premorbid fitness

and health were even better than healthy people and

people with irritable bowel syndrome. Either CFS

individuals are fitter, stronger, and healthier before

they get ill or their perceptions of normality change

during the time they are ill.

The Autonomic Nervous System During Exercise

People with CFS are as unfit as healthy but sedentary

people. Although CFS patients are as unfit as sedentary people, sedentary people tend to be sedentary

most of their adult lives; people with CFS have

become sedentary. Wessely, Sharpe, and others have

suggested a cognitive behavioral model of CFS: it is

well known within the field that dysfunctional illness

CNS and ANS Responses to Exercise in Patients with CFS

Peter D. White, M.D.
beliefs and avoidant coping perpetuate both the

symptoms and disability of CFS. One of the beliefs 

of CFS patients that predicts outcome is that exercise 

is dangerous or damaging. It is possible that this leads

to fear of exercise, an exercise phobia. CFS patients 

not only avoid exercise, but also they may avoid it

because of a fear response that may be autonomically mediated. 

If CFS is a classically conditioned exercise phobia, 

situational fear, avoidance, and autonomic nervous

system arousal could be expected. CFS patients may

avoid exercise and express a fear of exercise because

of a rational fear of having a relapse. To test for

excessive arousal, we measured electrical skin resistance during an ordinary day and during an exercise

test. The 42 study participants with non-comorbid

CFS were compared with healthy sedentary controls

matched in various ways. During the second day of

the study, participants exercised on a treadmill and

researchers measured activity with an ankle accelerometer, heart rates, and galvanic skin responses (GSR)

(the measure of electrical resistance across the palm,

which is related to the level of physiological arousal).

No difference in GSR was seen between people with

CFS and healthy sedentary controls, both during an

ordinary day and during exercise; they were no 

more aroused than controls.

CFS probably is not an exercise phobia. However, the

severity of both fatigue and disability was associated

with illness beliefs, deconditioning, perceived exertion,

and sensitivity to physical symptoms. Prospective studies also suggest that fitness, beliefs, and sensitivity are

predictive of outcome in CFS and are not merely

associated with it.

Exercise, the CNS, and Hormones

The effects of exercise on the brain are many: the

brain becomes more active and exercise elevates 

concentrations of the neurotransmitters serotonin,

dopamine, and norepinephrine, as well as beta-endorphin, prolactin, ACTH, and cortisol. More intriguingly, exercise increases brain-derived neurotrophin, 

a growth factor for the brain. Acute exercise has a

small enhancing effect on sleep, whereas persistent

inactivity causes poor quality sleep. Women in general

have longer, but less good-quality sleep and women

are generally less fit. It is possible that these two factors may help to explain why women get CFS more

often than men. Exercise is a stressor for people who

are physically unfit, with excess cortisol response,

while inactivity downregulates cortisol receptors.

Being unfit therefore affects hormones and produces 

an excessive stress hormone reaction. However, it

may also be true that people who have a generally

impaired HPA axis become fatigued when unable 

to exercise. In a patient with CFS, Sharma and colleagues showed that the excessive prolactin response

to buspirone reverted to normal after graded exercise

therapy, suggesting that this effect may be secondary

to inactivity and thus reversible in some people.

CFS probably is not an exercise phobia.

Shephard has reviewed how exercise induces an

inflammatory response, depending on endurance 

and exertion, and how exercise induces both a proinflammatory and an anti-inflammatory cytokine 

cascade. This response is exaggerated in unfit people.

Interleukin-6 is produced by both glial and muscle

cells during exercise. Could CFS be caused by an

excessive cytokine response to exercise? Patients 

with CFS have normal serum cytokine levels, on 

the whole, but not all cytokines have been studied.

Post-exercise cytokine levels are similar to preexercise levels, but the “exercise” involved may 

have been insufficient. Jones and colleagues recently

used a bicycle exercise test and found that a complement component increased after exercise in CFS

patients more than healthy controls. 

TNF-α not only increases with exercise, especially 

for unfit individuals, but it also increases with stress.

In a study just published, Steptoe and Owen looked

at healthy people having a stressor (a psychological

test) and found that those who had the highest heart

rate response to the stressor—those who were the

most stressed—also had the highest TNF-α response.

This result indicates that exercise and mental stress

may induce similar cytokine responses; two different

stressors may have the same physiological and pathophysiological effect. This might explain why patients

with CFS respond poorly to both physical and mental

stressors, although the evidence is so far not available.

Abnormal Introspection in CFS

Repeated studies that have compared subjectively

reported disability with objectively measured activity

in people with CFS show a discrepancy between

them. CFS patients complain about inability to concentrate and problems with memory but, when tested,

the results of cognitive testing tend to be essentially

42 CNS and ANS Responses to Exercise in Patients with CFS
CNS and ANS Responses to Exercise in Patients with CFS 43

normal. There are discrepancies between reported

abilities and objective ability tests in activity, effort

with exercise, sleep quantity and quality, and cognition. A study published last month by Smith and

Sullivan suggests that beliefs are part of that discrepancy. These authors gave benign chemicals blindly to

people who had CFS and who also believed they had

multiple chemical sensitivity. Individuals who believed

they were getting the chemical performed poorly on

cognitive tests, whereas there was no difference in

cognitive function between those who actually

received the chemicals and those who did not. 

The belief determined the brain reaction to the 

task more than the chemical itself; the perception 

was more important than the chemical.

Hypotheses To Be Tested

Four hypotheses can be gleaned from these studies:

1. Post-exertional fatigue or malaise is caused by 

an excessive cytokine cascade, itself related to

altered activity, deconditioning, and sleep 

disturbance (see Figure 1).

2. This reaction may be triggered by certain 

infections, but is maintained by a conditioned

response to exercise (see Figure 1). 

3. The symptoms of CFS are caused by CNS 

mediated interoceptive hypersensitivity, in 

a similar way to chronic pain syndromes, 

perhaps through classical conditioning. 

4. This introspective hypersensitivity is related 

to poor sleep, inactivity, and deconditioning,

through consequent neuroendocrine and 

cytokine links (see Figure 2).

Conclusion

A biopsychosocial model is more useful than 

a biomedical model in understanding CFS. The 

neuroimmune-endocrine abnormalities of CFS may 

be maintained by a conditioned response to activity 

and exercise (a testable hypothesis). This may explain

why a gradual return to avoided activity, common to

both graded exercise therapy and cognitive behavior

therapy, helps the majority of patients with CFS.

Discussion

Dr. Morens: If people with CFS are conditioned to be

physically fit, the heart rate goes down. Does their

perception of effort change after conditioning? After

conditioning, there is a discrepancy between heart

rate and actual performance. Does the perception of

effort correlate with the heart rate or with the actual

work done?

Dr. White: Both occur. Although RPE shifts back 

and a training effect occurs, no association was 

found between patients feeling better and actual 

physiological improvements of conditioning. It may

be that this is CNS desensitization to the perception

of effort, rather than simply being a training effect. Figure 1

Figure 2
Dr. Buchwald: Do you know of any studies that 

looked at perceptions such as vision, hearing, or 

taste in which standardized perception measures 

are available?

Dr. White: One study on visual sensitivity, which

some CFS patients report, did not find an association

with physiological evidence for visual sensitivity. 

This area is unexplored.

44 CNS and ANS Responses to Exercise in Patients with CFS
Corticotropin-Releasing Hormone, Insomnia, and Depression 45

I

nsomnia is a broad term that is generally defined

as a complaint of inadequate sleep despite adequate effort. From a clinical or treatment standpoint, insomnia is classified in two broad categories:

secondary and primary. Sleep disruptions associated

with CFS and other disturbances are secondary

insomnia. Anything that causes disturbed sleep and

sleep complaint is secondary insomnia, including

chronic pain, a variety of neurologic conditions, or

cardiovascular disease. Primary insomnia is a diagnosis of exclusion. As investigators try to characterize

the pathophysiology, the distinctions become spurious: many of the effects and symptoms associated

with primary insomnia can be found in people who

have secondary insomnia. Depression is a good example: 80 to 90 percent of people who are depressed

have sleep disturbance. Even though that may be 

a secondary insomnia, many features of it are 

characteristic of primary insomnia.

Primary insomnia is a common disorder. About 10

percent of adults over the course of a year will have

significant insomnia and a large percentage of those

are primary. There is gender- and age-dependent

prevalence: insomnia increases with age and is more

common in women. A clear relationship to stress

exists, in both precipitation and ongoing insomnia

complaints. It has a chronic, recurrent course: data

indicate that people with significant primary insomnia,

lasting 2 weeks or longer, have a lifelong condition.

Insomnia is linked epidemiologically to major depression. Data indicate that people who have significant

primary insomnia and no other symptoms have a

much higher risk of developing major depression in 

3 to 4 years. People who have one of the major psychiatric disorders are likely also to have insomnia.

Physiologic hyper-arousal is specific to primary

insomnia, which may be relevant to CFS. Patients

who complain of insomnia of significant duration

typically experience insomnia for at least 3 months.

Several lines of evidence from different individuals

support hyperactivation of the sympathetic nervous

system, also called autonomic arousal. A study by

Bonnett shows that basal metabolic rate is higher in

primary insomniacs relative to age-matched controls.

Relevance to sympathetic nervous system activation

may be weak, but data from Lushington shows that 

a group of insomniacs compared to a group of controls had higher body temperature, independent of

sleep disruption that characterizes that population.

Heart rate and the low frequency/high frequency 

ratio are higher in patients with primary insomnia.

Data from Stepanski indicate that, at any given point

for the control state and for the sleep state, heart rate

is higher in patients with primary insomnia. Studies 

of spectroanalysis of R-R (electrocardiogram R wave)

intervals show that sympathetic activation occurs to 

a greater degree in patients with primary insomnia

than in normal controls.

Physiologic hyper-arousal is specific 

to primary insomnia, which may be 

relevant to CFS.

In a study by McClure on catecholamine data, ten

patients with primary insomnia, in 24-hour urine collections at baseline, were shown to have significantly

higher levels of norepinephrine and indistinguishably

higher levels of epinephrine. Characteristic of much of

the research in the field is that baseline values appear

to be only mildly affected. (Vgontzas and colleagues

recently showed, with 24-hour urinary norepinephrine levels, a correlation between the degree of norepinephrine elevation and the severity of insomnia.)

McClure used a modification of the Trier Social 

Stress Test, which measures the remarkable activations, principally of cortisol, in anticipation of a public speech—a broadly applied psychological stressor.

In a 3-day paradigm, subjects were admitted to the

Corticotropin-Releasing Hormone, Insomnia, and Depression

Gary S. Richardson, M.D.
laboratory and told they would be part of a study 

on stress levels and sleep. Ten subjects were primary

insomniacs and seven were normal controls. Without

forewarning, subjects were approached on the evening

of the third night and asked if they would be interested in participating in another study. If they agreed to

this second study, they were taken to a large auditorium the evening before the third night and were given

three difficult speech topics to choose from, with minimal supporting papers. They were then left alone 

for an hour, and then brought back to bed. Many 

of these subjects did not sleep the entire night. They

got up the next morning and were taken to a conference room with five psychology interns sitting around

a conference table with a video camera, and were

then asked to give their speech.

The Multiple Sleep Latency Test (MSLT) is a measure

of how sleepy a person is. It is an objective recording

of the polysomnographic parameters, to record the

exact moment at which a person falls asleep under

standardized conditions. The longer it takes to fall

asleep, the more alert the person is. MSLT urine 

data after the public speech showed that epinephrine

levels were unchanged in the normal population but

changed significantly in the insomniacs; these people

were unimpressively different at baseline despite having relatively severe insomnia.

As a result of McClure’s study, the model under consideration is that this is a group with a hyperactive

stress response and, in particular, an inability of that

response to restore normal levels in stress indexes

after the stressor is removed.

In another study using the MSLT, Stepanski looked 

at 45 normal individuals and 70 insomnia patients

who had the same bedtimes but not the same amount

of sleep. The MSLT was higher in the insomniacs relative to the normals even though they got less sleep;

this shows that the MSLT is sensitive to a full-day

physiologic hyper-arousal and that the elevated levels 

of arousal translate into longer sleep latencies.

In McClure’s paradigm using the MSLT before 

and after the public speech, normals start off worse

but insomniacs and normals show the same decrease 

in sleep deficiency in response to the public speech.

What predicts the percentage drop is less related 

to insomnia than to how much the subject dislikes

public speaking. Both controls and insomnia patients

have substantially worsened sleep the night before the

speech. As soon as the speech was over, participants

were sent back to their rooms to watch television.

The normals collapsed and showed increased levels 

of sleepiness. However, the MSLT scores of the

insomniacs increased; they were more physiologically aroused by this experience even after the 

experience was over. This concept is crucial and 

central to the pathophysiology of primary insomnia.

Sympathetic activation seems to alter

perception of what is occurring.

Another study investigated whether or not this 

physiological arousal is primary or secondary to 

the insomnia. Data from other studies suggest that

chronically disrupted sleep produces physiologic

arousal: as a tool to explore hypertension, Gordon

used acute dietary salt restriction, which produces 

an activation of the sympathetic nervous system 

with increases in catecholamines, and in 1983 

Ditiello used acute dietary salt restriction to produce sleep disturbance in normal individuals, 

concluding that it made them look like they were 

old. With these and other studies as background, 

Dr. Richardson studied 11 healthy young adults 

for 6 days and nights in the sleep lab. Subjects 

were fed a regular hospital diet on day zero (greater

than 100mEq of sodium a day), and then they were

given a very low sodium diet of less than 17mEq for

days 1 through 5. There was some concern about

occasional episodes of orthostatic hypotension in 

this setting; therefore, vital signs were monitored

throughout. Norepinephrine did not increase significantly. The assumption that all Americans have 

a high-salt diet may be a fallacy, so a new study 

has been undertaken in which all participants 

are salt-loaded up front.

A modest increase in norepinephrine levels was 

seen, and some individuals had significant increases 

in norepinephrine levels. All participants showed a

significant decrease in sleep efficiency and a significant increase in the time it took them to fall asleep. 

In addition, the amount of lightest, least restorative

sleep (Stage One) also increases with salt restriction.

Although not statistically significant, there is a 

correlation between the degree of norepinephrine 

elevation and these measures.

One of the cardinal tenets about primary insomnia 

is that insomniacs see their insomnia as much worse

than it really is. In this study, normal individuals

started out being reasonably accurate at estimating

46 Corticotropin-Releasing Hormone, Insomnia, and Depression 
Corticotropin-Releasing Hormone, Insomnia, and Depression 47

sleep latency, number of wakes, and the quality of

their sleep at baseline. However, all of them registered

increases in what they thought would happen that

were much greater than what was actually happening,

particularly in sleep latency measures. One of the conclusions from this study is that sympathetic activation

seems to alter perception of what is occurring. The

modest increase in sleep latency, despite the sleep 

disruption, is reminiscent of primary insomnia.

Assuming that the responsiveness of catecholamines 

is abnormal in insomniacs, one of the implications 

is that the hypothalamic-pituitary-adrenal (HPA) axis

should be affected. We will attempt to implicate the

corticotropin-releasing hormone (CRH) neuron in 

the hypothalamus, one of the tests of which will be

the appearance of abnormalities in the HPA axis.

Whether HPA function is abnormal in primary 

insomnia is the focus of Penn State researchers who

are working on a similar model. They have found a

significantly higher basal cortisol level without any

stimulation in patients with primary insomnia versus

normal controls. Vgontzas showed that patients with

worse insomnia had higher urinary-free cortisol. 

We have begun a study that uses the Dex CRH 

Test in which subjects are given dexamethasone the

night before the test to create comparable degrees of

suppression; their systems are then stimulated with 

exogenous CRH at time zero. To date, ten normals

and three patients have been studied. The first three

subjects do not show escape at baseline but do show

an impressive increase in ACTH, much more than 

cortisol, in response to Dex CRH. In combination,

these data support the idea that the HPA axis 

and the sympathetic outflow are abnormal in 

insomnia patients.

Stress precipitates or perpetuates primary insomnia.

Several longitudinal studies have shown that stress 

is an important factor in primary insomnia. If it is

true that CRH is important to depression, then the

fact that insomnia is linked both epidemiologically

and syndromally to depression supports the idea 

that CRH is involved in insomnia. In several preclinical animal studies, CRH was shown to mimic

many of the symptoms associated with primary

insomnia. Data support the idea that throughout 

the brain locations for CRH, this peptide serves a 

relatively singular integrative function—it seems to 

be involved in mediating or integrating the stress

response. When CRH is injected around the brain

stem, EEG desynchrony is produced, which can be

characterized as wakefulness. Studies with antagonists show that CRH increases wakefulness at the 

circadian wakefulness bays and, in particular, in 

the setting of stress-induced insomnia.

Opp and colleagues conducted a study of stressinduced insomnia in which socially isolated rats

showed a decrease in the amount of sleep. In grouphoused individuals infused with the CRH antagonist,

no net effect was seen. However, in stressed animals,

the stress-induced decrease in sleep and the alphahelical CRF (the antagonist) restored sleep levels 

to near normal. Several active investigations are 

now using CRH antagonists in humans to find 

out if these drugs can inhibit stress-induced insomnia without producing sedation when stress 

is not present.

Stress precipitates or perpetuates 

primary insomnia.

Pivagabine is a drug associated with a decrease in

CRH release. In individuals with insomnia in the 

setting of psychiatric disease, pivagabine is associated with a substantial improvement in insomnia 

independent of the change in the underlying 

psychiatric disease.

Several researchers have suggested that catecholaminergic tone in particular (and sympathetic outload generally) has an ideal set point, which is not 

zero and not maximal but somewhere in between. 

A convergence occurs when looking at CNS effects 

of pushing that system away from its set point in 

either direction. One of the challenges is to understand how researchers can be working in what 

seem to be opposite directions and yet end up 

with many similar outcomes.

Discussion

Dr. Crofford: I am intrigued by perception versus

reality, a disconnect being described by several 

people. What kinds of chemical mediators or cortical sites might be creating this? Some people have

talked about norepinephrine as potentially mediating

this and some have talked about CRH. Does anyone

know the neuroanatomical localization of perception, which seems to cross many different symptom

domains? Does anyone know whether or not it is 

norepinephrine-predominant or CRH-predominant?

A perceptual axis is presumed in cortical sites.
48 Corticotropin-Releasing Hormone, Insomnia, and Depression 

Dr. Park: Explicit recollection is largely in the 

frontal cortex. It is possible, but not necessarily 

plausible, that CFS patients have some kind of 

frontal dysfunction. Instead of relying on what 

they explicitly remember, they rely on what they 

feel or what feels familiar. People are talking more

about beliefs than about perception. The discussion largely revolved around people saying they

believe something is true, and that belief is just 

disconnected from their behavior. A belief is 

different from a perception. A perception should 

have a sensory analog in the visual cortex or the 

auditory cortex.

What presenters have shown today is malleability in

neurochemical systems, but no equivalent behavioral

work has been presented thus far. More responsivity

to emotional stimuli would be expected at the neurological and behavioral levels in a CFS patient who

exhibits neurobiological reactivity. Patients have 

been well characterized neurobiologically, but not

well characterized behaviorally.

Dr. Clauw: This spectrum of illness may well be a

problem with interoception and more than just pain

or other symptoms. People with CFS or fibromyalgia

have shown a poor relationship between, for example, their self-reported physical activity and objective

measures or between self-reported cognitive function

and what is measured. That result is also true of controls—many of these disconnects are equally true in

control populations.

Bud Craig is focusing on the anterior insula as being 

an area of interoception. There is a great deal of 

converging evidence from both animal models and

human trials with, for example, dyspnea and other

unpleasant sensations. The neurochemistry is not 

as well characterized as the neuroanatomy, but 

many researchers are focusing in this area as 

possibly being an anterior septa varum.

Dr. White: At Kings, a group of researchers 

used an activity intervention after mononucleosis 

to prevent abnormal fatigue for 6 months; results

show a 50 percent drop in fatigue in 6 months. It 

was only a pilot study, but 69 patients were studied.

If a grant is won, a larger study will begin. Patients

were encouraged to become more active in a graded

way within a month of the onset of their infectious

mononucleosis. In 6 months, the complaints of

fatigue were reduced by one-half.

Dr. White: The two first studies of CBT for CFS 

were successful. In Sharpe’s study at Oxford and

Wesley’s study at Kings, there was no change at the

end of treatment compared to the two control groups

(one receiving usual care and the other controlling 

for therapist time). However, 8 months later as they

became behaviorally more active, desensitization

occurred and there was a change from the placebo

groups. Symptoms and disability both improved. The

beliefs had changed but their behavior, symptoms, and

disability had not changed. Only when subjects were

persuaded to become more active did they get better.

What presenters have shown today is malleability in neurochemical

systems, but no equivalent behavioral work has been presented thus

far. More responsivity to emotional stimuli would be expected at the

neurological and behavioral levels in a CFS patient who exhibits 

neurobiological reactivity. Patients have been well characterized 

neurobiologically, but not well characterized behaviorally.
Cytokines, Sleep, and the CNS 49

Session Three: Cytokines, Sleep, and the CNS

Chair: Harvey Moldofsky, M.D.

One of the recurrent themes related to chronic fatigue syndrome heard throughout this workshop 

has been poor sleep—problems falling asleep, staying asleep, or waking feeling unrefreshed. 

What happened, or the perception of what happened, during the previous night affects how 

people feel the following day in terms of fatigue, cognitive problems, and autonomic disturbances. 

Apparently, there is something compelling about sleep, as well as how the sleeping and waking brain 

is related to regulatory functions involving cytokines, neuroimmune, and neuroendocrine functions.

Genetics of Sleep Regulation 51

S

leep is a ubiquitous biological phenomenon. 

It has been described in all mammalian and 

avian species studied to date, and sophisticated

genetic studies are now beginning to explore the

genetic basis of sleep in animals such as Drosophila,

nematodes, and fish. The field of genetic regulation 

of sleep is expanding rapidly.

Humans spend about one-third of their lives asleep,

and some animals (for example, cats) spend twothirds or more of their lives asleep. Despite all the

time devoted to sleep, ideas about what sleep does 

for the body remain controversial, with lively ongoing debate about questions as fundamental as

whether the functions of sleep are understood. 

The field of sleep has made considerable substantive progress in the past 10 years, developing from 

what was considered a soft science to what is now

seen as cutting-edge brain neurobiology. Genetics

have helped move the field in this direction.

Sleep problems and alterations in sleep are not confined to people with chronic diseases. Many people

suffer at some time in their life from a sleep problem,

either inability to stay asleep or inability to experience

refreshing sleep. For some patients with chronic diseases, these problems can become debilitating. This 

is being recognized increasingly as treatments are

developed for diseases, such as hepatitis and HIV,

once relatively acute and potentially fatal but now

persistent and chronic. In many of such patients, 

perhaps because of their treatments, among their

major complaints are problems with sleep or nonrestorative sleep or fatigue. 

In the state of infectious disease, a putative reason 

for going to sleep is apparent, at least on an anecdotal

basis. Many people have experienced acute infectious

diseases, such as a cold or influenza, and during these

times most have felt either an increased desire to sleep

or, depending on the stage of the disease, an inability

to sleep. There is an almost intuitive feeling that 

sleep has some curative or protective properties. 

Most people have said or heard the following: 

“You had better get some sleep or you will never

recover” or “If you do not get some sleep, you 

will become ill.” There is a sense that sleep and 

the immune response are related and that sleep 

can aid recovery from infectious diseases.

In 1988, there were few empirical data to show 

that sleep changed in any way over the course of 

an infectious disease. Since then a body of data 

has accumulated showing that sleep does change 

during infections. Some are self-reports in human

studies but some have also been followed up

polysomnographically. In animals, researchers 

rely on polysomnographic reporting to indicate

whether the animals are awake or asleep. 

Sleep does change during infections.

A wide variety of infectious challenges have been 

tested and found to cause robust changes in normal

spontaneous sleep patterns. For example, in the 

rabbit model, bacterial, fungal, influenza, viral, and

even protozoal infections can influence the immune

response and the sleep response. These responses 

are modulated by the basal immunologic state of 

the animal; environment, hormonal status, circadian

cycle; and other features affect the type of response.

We have worked extensively with mice infected 

with influenza virus. In the basic experimental 

design, the mice undergo surgery and are implanted

with electroencephalogram (EEG) and electromyogram (EMG) recording electrodes, so that recorded

EEG data can be used to score sleep. After a 2- to 

3-week recovery period, their sleep is studied for 

1 to 2 days and then they are inoculated intranasally

with influenza. This model gives the mice an upper

Genetics of Sleep Regulation

Linda A. Toth, D.V.M., Ph.D.
respiratory tract infection and a pneumonia from

which they would typically recover in 7 to 10 days; 

it is analogous to a severe human cold, except that 

the mice also get pneumonia. Usually the mice are

euthanized 3 to 4 days after infection, so that various parameters can be measured.

One of the strains of mice utilized in these investigations is the inbred C57BL/6J; those inbred mice are

selectively brother/sister-mated for at least 20 generations. Studying an inbred mouse strain is considered

analogous to an unlimited twin study with many 

genetically identical animals. Working with a complicated phenotype such as sleep, this makes it 

possible to get an average phenotype for a fixed 

genotype. The hundreds of strains of inbred mice 

are part of the armamentarium to try to dissect 

the genetic basis for many complex traits, such 

as infection-related changes.

In their basal sleep patterns, C57BL/6J mice showed 

a marked circadian rhythm, sleeping more during 

the light phase and becoming nocturnally active 

when lights were off. In mice inoculated with allantoic fluid, no marked changes were observed in sleep

patterns. However, within about 18 hours, mice inoculated with influenza virus began to show a marked

increase in the amount of time they spent asleep. 

The increase was most pronounced during the dark

phase when the mice would normally be awake, 

representing loss of the circadian rhythm of sleep. 

The mice essentially slept the same amount of time 

all the time—behaviorally equivalent to a person 

getting sick with a cold or flu and staying home 

from work and sleeping all day. This is essentially

equivalent to an excessive daytime sleepiness 

response in people.

The many strains of inbred mice exhibit substantial genetic differences. The C57BL/6 strain and 

the BALB/c strain vary in a number of immune

response parameters. For example, C57BL/6 mice

tend to show a cytotoxic T1 cell response more 

predominately, while BALB/c mice are T2 responders. The two strains have different major histocompatibility complex haplotypes. IF1 genes, which 

control interferon production and respond differentially in a variety of paradigms, are different.

Any of these differences—and potentially many 

others—could theoretically influence how these 

mice sleep after microbial challenge.

Like C57BL/6 mice, infected BALB/c mice showed 

a loss of the circadian rhythm of sleep; however,

rather than developing increased sleep, they showed

reduced sleep during their normal period of somnolence. When they should have been resting or 

sleeping, they exhibited instead an insomnia-like 

phenotype. Immunized C57BL/6 mice rapidly 

cleared the virus and their sleep patterns quickly

returned to normal, whereas immunized BALB/c 

mice still showed a tendency to sleep a bit less 

than before. 

These characteristics are shared by many inbred

strains of mice. A survey of nine strains found 

several that, like BALB/c, showed a reduction in 

sleep during the light phase of the cycle during 

infection. Other strains, such as C57BL/6, showed 

the daytime sleepiness phenotype. These two patterns of change in sleep response to one particular

infectious challenge seem to be fairly common 

across a variety of different inbred strains of mice.

Influenza is not the only infection with this effect. 

In mice with nephritis caused by Candida albicans,

changes occurred in both slow-wave sleep and REM

sleep. In a model of immune-mediated hepatitis

caused by injecting mice with Concanavalin A, 

strain differences in sleep also occurred. The sleep

patterns of A/J mice did not change, BALB/c mice

showed a moderate increase in sleep time, and

C57BL/6 mice showed an even greater increase.

These two patterns of change in sleep

response to one particular infectious

challenge seem to be fairly common

across a variety of different inbred

strains of mice.

Two approaches have been used to study the cause 

of these responses. The first is gene-driven, with the

general hypothesis that a particular gene influences

the expression of the sleep phenotype. The tools 

used to study the impact of known or potential 

sleep regulatory substances on the sleep pattern 

are often induced or spontaneous mutant mice, 

drugs, or antibodies. One example is the study of

interferon-α as the candidate substance for influenzarelated enhancement of sleep. Because it is known 

to induce sleep, interferon-α is a potential mediator

52 Genetics of Sleep Regulation
Genetics of Sleep Regulation 53

for increased sleep during infection. It is the classic

antiviral cytokine known to be produced in large

amounts during at least the early stages of viral 

infection, and the IF1 gene in mice genetically 

controls it. C57BL/6 mice have the allele for high 

production so they make more interferon, which

could cause excessive sleep; BALB/c mice have 

the allele for low production and therefore could 

have impaired sleep.

Whether the IF1 allele causes these divergent 

responses can be tested in congenic mice strains,

which are bred to have the genetic background 

of one strain with a small genetic segment that is

selectively bred into the background strain from 

a donor animal. In this study, a strain of congenic

mice was developed with the H28 histocompatible

antigen from BALB/c mice bred onto the C57BL/6

genetic background, the result being a mouse that 

is 99 percent C57BL/6 but has one genetic segment

from BALB/c that also contains the IF1-low allele.

When tested, the IF1-low allele was not found to

influence the sleep pattern in the model. The C57BL/6

mice with the high allele showed increased sleep, and

the C57BL/6 mice with the low allele also showed

increased sleep. Neither group looked like the BALB/c

mouse, indicating that the interferon allele is not 

critical to the high-sleep phenotype in this model.

When mice were injected with Newcastle disease 

virus (NDV), the C57BL/6 mice again showed highsleep phenotype, the BALB/c mice still showed a 

relatively low-sleep phenotype, and the response of

the congenic mice was similar to that of the BALB/c

mice. In this case, the IF1-low allele did seem to be

correlated with the sleep response, allowing the conclusion that the role of the IF1 gene depends on the

challenge. The IF1-high allele did seem to promote

NDV-induced sleep but did not influence influenzainduced sleep, an indication that other factors must

mediate the hypersomnolence or hyposomnolence

seen in mice with influenza infections. This series 

of studies illustrates how specifically bred mice can 

be used to determine the contribution of a specific 

gene to a complex behavioral phenotype.

With interferon-α eliminated, one strategy is to 

continue examining factors that could influence

sleep, for example, known somnogens such as IL-1

and TNF, and test them individually in order of 

priority to determine whether they influence the 

phenotype. Another strategy is a genome-wide

search, which is essentially phenotype driven and

looks for the genes that affect phenotype expression. Instead of focusing on one specific gene or 

substance, the focus is on the phenotype, without a

priori assumptions about mechanisms. The genomewide search can be conducted in a variety of ways,

including random mutagenesis, microarrays, and 

proteomics. These searches can survey the entire

genome for differences related to a particular 

condition or phenotype in an animal or human.

Our approach to genome-wide searching used 

linkage analysis in recombinant inbred mice. These

mice are produced by crossing two progenitor strains

that differ in some particular trait; the offspring are

then inbred through 20 generations. At 20 generations, each mouse is essentially homogeneous for all

the alleles. Each has a random fixed assortment of 

all the parental alleles, allowing determination of

average genotypes for each fixed phenotype. These

mice are valuable tools for mapping complex traits,

and many strains are commercially available. 

This series of studies illustrates how

specifically bred mice can be used to

determine the contribution of a specific

gene to a complex behavioral phenotype.

The first step of the mapping study was to determine the phenotypes of each strain being studied. 

The next step was to look for correlations between

the phenotypes and the distribution of alleles at 

marker loci, and then the task was to estimate 

the probability of obtaining those correlations. 

We used this procedure to analyze 13 recombinant

inbred strains of mice derived from C57BL/6 and

BALB/c parents. This analysis showed a strong linkage of the light-phase phenotype of reduced sleep—

essentially, the insomnia phenotype—to a certain

region of chromosome 6.

Quite a few genes that might influence expression of

this trait were found in the region of chromosome 6.

CD8-α is a T-cell antigen that influences the immune

response. The ADCYAP receptor has been related to

REM sleep regulation. Other candidate genes were

neuropeptide Y, growth hormone-releasing hormone

receptor, and CRH receptor 2. This genome-wide

approach results in a short list of strong candidates.

Instead of needing to study 100 candidate genes 

that might influence a trait, investigators can focus 

on only a few.
Thus, strategies for identifying sleep regulatory genes

in mice are at least dual: the genome-wide search can

allow identification of candidate mechanisms for complex phenotypes, followed by a gene-focused approach

that can test the contribution of potential candidates.

Mice are not the same as humans, but animal studies

provide suggestions on how to move forward and

what might be useful to study. One example is pinpointing orexin as the genetic lesion that causes narcolepsy in dogs. This was done by Minot’s group 

in 1999 by genotyping a population of dogs that

spontaneously displayed narcolepsy and conducting 

a genetic analysis similar to what might be done in 

a human population. The work in dogs was corroborated 2 weeks later by a group working in parallel

using a mouse with some part of the orexinergic 

system knocked out; they saw narcoleptic phenotypes in mice. The mice would walk in the cage and

suddenly fall over in a cataplectic state, and within 

a few minutes get up and walk around again. This

was revolutionary for the field of sleep medicine

because it has tied in a particular genetic abnormality to a sleep phenotype. In one study, as many as 

90 percent of human narcoleptics had a deficiency 

in orexin. It is not likely that this gene would have

been examined for relation to a sleep disorder had

not the genetic mechanism first been elucidated in 

an animal model. Thought to be involved in food

intake, orexin was initially investigated in the knockout mice to study energy homeostasis, and it suggested

a link between energy balance and regulation of sleep

that has spurred a remarkable number of investigations in the sleep field.

These types of genetic influences can also be detected by looking at spontaneous sleep apart from sleep 

disorders. Rab3a is a gene involved in synaptic 

plasticity; about a year ago it was reported to be

involved in not only circadian rhythms (shortening 

of the circadian day) but also in sleep homeostasis

(the rebound response to sleep loss). Rab3a was

known but researchers did not connect it to a sleep

homeostatic mechanism until a random mouse mutagenesis study detected altered circadian rhythms, and

then found that the defect in the random mutagenesis

was probably in the Rab3a gene—highly suggestive

that the Rab3a gene is involved in sleep regulation.

Many other studies have shown that various spontaneous and induced mutations are associated with the

regulation of spontaneous sleep in a variety of animal

models, and some of these have been extended into

human studies using various challenges.

Fatigue is more challenging to describe in animals

than is sleep. In animals, sleep can be measured 

but no simple way to measure fatigue has been developed; people can report fatigue but animals cannot.

Increased sleep may suggest fatigue, because sleep 

can be a response to fatigue; an organism—animal 

or human—might sleep more because it is tired all 

the time. However, inadequate sleep or inability 

to sleep soundly may also cause fatigue. Using locomotor activity as a measure of sleep or fatigue can

also be confounding in many cases. For example, 

an organism could be too fatigued to move much, 

but might still be unable to sleep or fall asleep. 

Using voluntary activity such as wheel running 

might work and has been tried, but such work

remains preliminary.

In one study, as many as 90 percent 

of human narcoleptics had a deficiency 

in orexin. It is not likely that this gene

would have been examined for relation

to a sleep disorder had not the genetic

mechanism first been elucidated in an

animal model.

Influenza-infected C57BL/6 and BALB/c mice that

have been immunized illustrate the complexities of

these studies. The C57BL/6 mice quickly return to

their normal sleep patterns, while the BALB/c mice

show slightly less sleep. Locomotor activity and 

temperature patterns, however, show two different

responses. The C57BL/6 mice resumed their normal

sleep patterns, but they remained hypoactive and

hypothermic (mice with infections tend to become

hypothermic rather than febrile). The C57BL/6 mice

took a longer time to recover completely from the 

flu, while the BALB/c mice recovered in a day. 

Speed of recovery may be related to a specific 

genetic response.

In studying fatigue, the basic question is what 

constitutes an appropriate phenotype. Only when 

an appropriate phenotype for fatigue is described 

can mechanisms be addressed, either by looking 

at candidate gene approaches or by using genomewide approaches. In some cases, sleep may be an

appropriate substitute for fatigue, but researchers

need to be more inventive to arrive at accurate 

methods for assessing fatigue. The many different

54 Genetics of Sleep Regulation
Genetics of Sleep Regulation 55

types of fatigue that have been described in humans

may or may not have correlates in animals.

It is hoped that identifying some of these genetic

mechanisms will help identify the pathophysiologic causes of fatigue, excessive sleepiness, and 

nonrestorative sleep in a similar manner to the 

recognition of the role of the orexin gene in narcoleptic dogs. With this knowledge, the next step 

will be to develop interventions that will help 

control or prevent these symptoms, just as orexin 

has become a new potential therapeutic intervention in treating narcolepsy.

Discussion

Dr. Buchwald: How much variability is there in 

sleep within a strain in terms of length or other

parameters, and has there been any research to

account for differences seen in sleep, given that 

these animals are genetically similar?

Dr. Toth: Some inbred strains diverge a great deal in

their normal sleep patterns. Variation within strains

also depends on the strain; some seem to be more

variable than others. Strains that vary more may be

more sensitive to factors in the environment, such as

temperature fluctuations or noise. About 35 percent

of the variation can be accounted for genetically.

Because of the variation within strains, characterizing a sufficient number of animals is needed to get 

an average phenotype for each strain.

Dr. Sternberg: Are there sex and gender effects?

Dr. Toth: I am not aware of any researchers who 

have looked at that in mice. Certainly there are 

such differences in rats in terms of sleep. I have

always used male mice and so has everyone else 

I am aware of, but I would be astounded if there 

were not also gender differences in rats.

Dr. Sternberg: What are the effects in rats? 

What are the sex differences?

Dr. Toth: Female rats change their sleep patterns as 

a function of the estrous cycle, which is why I have

hesitated using them. I have never compared females

to males. The males seem to be more consistent from

day to day. However, in females, the estrous cycle 

and pregnancy cause changes in sleep patterns.

Research suggests the existence of a biologic

basis whereby responses to immune challenge can be transduced into alterations 

and behavioral outcome measures, specifically, 

alterations in sleep/wake behavior. The questions 

to be addressed are the functional questions about

why individuals sleep and why people sleep differently when they are sick. Most individuals have 

personal experience with the changes in cognitive

well-being and behavior through the course of 

an infectious challenge.

In the course of an acute infection, the immune 

system detects the pathogenic invasion, and a 

variety of physiological and behavioral changes 

occur. The hallmark manifestation is the onset of

fever. If the systems and processes induced by the

pathogen function effectively and efficiently to 

inhibit the growth of the pathogen and return 

an individual to health, the infection will be 

resolved and life-as-usual resumed. 

In regulation of sleep/wake behavior,

every major neurotransmitter system

defined in the brain is involved at

some level.

The question of why people sleep differently when

sick can be addressed in two ways. A functional perspective considers whether this aids in recuperation

and whether people recover more quickly because 

of changes in sleep. A more mechanistic perspective

considers what happens to convey information from

the peripheral immune system to the brain that ultimately results in changes in behavior and physiological processes. While functional questions are important and ultimately should be addressed, elucidation

of mechanisms involved in altered behavior through 

the course of immune challenge is also critical.

Many systems are involved in sleep and other 

complex behaviors. There are many points of entry

whereby stimuli or alterations can change these systems and many points of exit in terms of behavioral

responses. In regulation of sleep/wake behavior, every

major neurotransmitter system defined in the brain is

involved at some level. Therefore, any alteration of

activity levels of those neurotransmitter or neuropeptide systems has at least the potential to alter

sleep/wake behavior.

Just as there are many neurotransmitter systems

involved in the regulation of sleep, many cytokines

are now known to be regulators or modulators of

arousal state. The two cytokines that have been 

studied to the greatest extent with respect to their

impact on sleep/wake behavior and their role as 

regulators of sleep are interleukin-1 (IL-1) and tumor

necrosis factor (TNF). A variety of other cytokines,

chemokines, and growth factors have been implicated at some level as modulators of sleep, but 

IL-1 and TNF have received the most attention.

Corticotropin-Releasing Hormone and the

Regulation of Wakefulness or Arousal

Many studies indicate that, directly or indirectly, 

corticotropin-releasing hormone (CRH) is involved 

in the regulation of wakefulness. Studies by Kalin 

and others demonstrate that there is a circadian

rhythm for CRH and that rhythms of CRH and 

HPA axis activity parallel periods when animals 

are awake or aroused. Administering CRH to an 

otherwise normal animal increases electroencephalogram (EEG)-defined wakefulness. When the CRH 

system is antagonized, EEG-defined wakefulness 

is reduced; rats deficient in CRH production also

exhibit less spontaneous wakefulness. If the system 

is targeted at the receptor level, the amount of 

time an otherwise normal animal spends awake 

can be reduced.

Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State 57

Cytokines–Neurotransmitter Interactions and the Regulation 

of Arousal State

Mark R. Opp, Ph.D.
Low doses of CRH administered into the lateral 

ventricle of rats, either prior to the beginning of 

the dark portion of the light-dark cycle or prior 

to the beginning of the light period, increase the

amount of time the animals spend awake. The 

proportional change in the amount of time they 

spend awake is greater if CRH is administered 

prior to the light period because this is the time 

when the animals normally sleep the most.

Lewis and Fischer rats differ in their production of

CRH and in HPA axis activity. With Lewis, Fischer,

and Sprague-Dawley rats, spontaneous sleep/wake

behavior in the absence of any other challenge (except

the surgical implantations that allow researchers to

determine sleep/wake behavior) was studied. The

Lewis rats, which have reduced CRH and which

exhibit hypo-responsive HPA axis activity, spend less

time awake during both light and dark periods of the

light-dark cycle. Therefore, reduced endogenous levels

of CRH in an otherwise normal animal are associated

with reductions in the amount of time spent awake.

Role of IL-1 in Sleep Regulation

Most cytokines to date have been described initially 

as products of the immune system. Although 20 years

ago the idea that cytokines could be produced within

the CNS was viewed with skepticism, now it is known

that cytokines and their receptors are found in the

brain. They have been implicated in many CNS

processes, including arousal state, thermoregulation,

appetite and feeding, sexual behavior, social interactions, and mood.

An abundance of evidence indicates that IL-1 is

involved in the regulation and modulation of sleep.

Starting in the early to mid-1980s, Krueger and colleagues demonstrated that administration of IL-1 into

rabbits increases the amount of non-REM (rapid eye

movement) sleep. Moldofsky and colleagues demonstrated that concentrations of IL-1 in human plasma

peak at sleep onset. In studies done in cats, IL-1-like

activity in the cerebrospinal fluid varied in phase with

sleep/wake behavior. When IL-1 is given to humans 

or laboratory animals, the amount of time spent in

non-REM sleep increases. Antagonizing the systems

reduces the amount of time spent in non-REM sleep.

Protein and message expression in the brain demonstrate diurnal rhythms that parallel sleep/wake behavior. If receptors are knocked out and they are not

challenged by any other means, laboratory animals

spend less time asleep.

One example of how IL-1 affects the sleep of rats 

is seen in an experiment with Sprague-Dawley rats. 

A standard dose (5 nanograms) of IL-1 was given

through intracerebroventricular (ICV) administration.

In the first hour post-injection, there was an increase

in the amount of time the animals spent in sleep, but

the bulk of increase in non-REM sleep occurred 4 or 5

hours after ICV administration. When IL-1 was given

before the dark period, REM sleep was suppressed for

4 to 6 hours. A typical response showed an increase 

in the amount of time spent in non-REM sleep.

The primary feedback mechanism for

cytokine synthesis within the brain is

the HPA axis, and it is the action of 

the glucocorticoids at the level of the

hippocampus and hypothalamus that

regulate synthesis of IL-1 and TNF.

The HPA axis is a critical negative feedback regulatory mechanism for many actions in the brain 

and for the regulation of immunomodulators, such 

as cytokines. If animals differ in their HPA axis

responsiveness to immune challenge, the precise 

sleep alterations in response to IL-1 will also differ

between these animals. Because Fischer rats are 

hyper-responsive to immune challenge, and Lewis 

rats are hyporesponsive with respect to the HPA 

axis, differential sleep responses are anticipated 

when each of these strains is injected with IL-1.

Fischer rats exhibited a clear difference from 

Sprague-Dawley rats; specifically, in the first hour

post-injection, no increase was seen in the amount 

of sleep time, and by the second hour post-injection,

the animals were awake nearly 100 percent of the

time. In comparing the Fischer rat responses to 

the responses of Lewis rats, it is clear that the time 

course of response was different. Animals that were

hyporesponsive and did not have an exaggerated 

HPA axis response in the primary negative feedback

regulatory mechanisms exhibited a rapid and dramatic

increase in the amount of time they spent asleep.

We hypothesized that the second hour pattern of

reduced sleep/enhanced wakefulness of Fischer 

rats after IL-1 was due to a CRH surge. When the

animals were pretreated with CRH receptor antagonist before the administration of IL-1, the pattern in

the first 2 to 3 hours after IL-1 administration was

completely blocked. No reduction in sleep after IL-1

administration was seen when CRH was blocked.

58 Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State 
Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State 59

Summarizing these experiments, if an animal is 

targeted with an immune challenge, there is an 

impact on HPA axis responsiveness and different

types of behavioral outcome measures depending 

on the direction of the HPA axis response.

If the HPA axis in an otherwise normal animal is 

targeted, with respect to cytokine systems, will anything change within the CNS or brain? Researchers

first targeted the HPA axis in an otherwise normal

animal. The primary feedback mechanism for cytokine synthesis within the brain is the HPA axis, and 

it is the action of the glucocorticoids at the level of

the hippocampus and hypothalamus that regulate 

synthesis of IL-1 and TNF. When the activity of the

system is high in a circadian rhythm, as in a rat with

the HPA axis activity highest during the dark period,

message levels for cytokines in the brain are reduced

because of this negative feedback inhibition.

We then investigated what would happen if the 

HPA axis were antagonized when at its highest level

of activity and the impact of glucocorticoids were

reduced within the CNS. The hypothesis was that

they would see an increase in synthesis in IL-1 at 

a time when it would normally be reduced. A CRH

receptor antagonist (astressin) was administered centrally into rats, which were then sacrificed 4 or 6

hours after administration. Tissues from the brain

were processed for message expression for a variety 

of cytokines, using ribonuclease protection. Samples

were taken from the hypothalamus, hippocampus,

brain stem, and cortex. It was readily apparent that

expression for IL-1 was dramatically increased in the

hippocampus, brain stem, and cortex of animals that

received the receptor antagonist, compared to those

that did not. Quantification of many samples showed

changes in both IL-1-α and IL-1-β in areas of the

brain that are responsible for the regulation of complex behavior, specifically sleep. We further demonstrated that the effects of intracerebroventricular 

(ICV) administration of a CRH receptor antagonist 

on sleep/wake behavior could be blocked completely 

if the animals were pretreated with an antibody 

directed against IL-1β.
Role of IL-6

New data about the role of IL-6 in the regulation 

of sleep/wake behavior are now available. Evidence 

is beginning to suggest that IL-6 may at least modulate sleep under some conditions. For example, it is

known that in response to IL-1 or TNF, many of the

behavioral and physiological outcome measures are

actually mediated by IL-6. Bauer demonstrated some

years ago that there is a rhythmic activity to IL-6 

concentrations in human subjects. When human 

volunteers are sleep-deprived, IL-6 increases. If IL-6 

is injected into human volunteers, the amount of time

they spend asleep increases during the latter portions

of the night. We recently reported that when IL-6 

was administered ICV into rats, there were periods 

of the recording time during which non-REM sleep

increased. It has been known for some time that 

IL-6 is a powerful stimulator of HPA axis activity.

Therefore, there are many reasons for interest in 

the sleep of IL-6 knockout mice.

One study compared the 24-hour pattern of body

temperature and non-REM and REM sleep in C57BL/6

mice and IL-6 knockout mice. The circadian rhythm

of body temperature is low during the rest period, 

or the light period of the light-dark cycle, and higher

at night when the animal is active. This was evident

and the amount of time spent in non-REM sleep and

REM sleep was charted. The compared data show

that there was no difference in timing of sleep in the

two strains, or in the rhythms of body temperature.

However, IL-6 knockout mice spent more time in

REM sleep than did the C57BL/6 mice. The amount

of time an animal spends asleep is one measure of

sleep/wake behavior. Another measure is the EEG,

which shows characteristic patterns and frequencies

during the different stages of sleep. In spectral analyses of EEGs from periods of non-REM or REM sleep

or wakefulness, the characteristic spectra did not differ between the C57BL/6 and IL-6 knockout mice. 

We then looked at how the mice responded to a

homeostatic challenge, specifically to periods of sleep

deprivation. If the C57BL/6 mice were sleep deprived

for 6 hours at the beginning of the light period and

then allowed to sleep normally after that deprivation,

rapid increases in the amount of time they spend in

non-REM and in REM sleep occurred. IL-6 knockout

mice subjected to 6 hours of sleep deprivation showed

a similar pattern; sleep deprivation affected their REM

sleep in the same manner as C57BL/6 mice. The effect

of sleep deprivation on non-REM sleep differed in

that the IL-6 knockout mice took longer to recover

after the deprivation period ended. The EEG correlates

after sleep deprivation show that the increase in intensity measures of sleep (the delta power) was identical

in C57BL/6 and IL-6 knockout mice. The IL-6 knockout mice slept normally when they were not challenged,

and they reacted similarly in response to a moderate

homeostatic challenge, such as 6 hours of sleep deprivation. Lack of a functional IL-6 gene did not seem 

to greatly affect any of the parameters studied.

Of greater interest is how the mice respond to an

immune challenge. After intraperitoneal administration of 10 micrograms of bacterial lipopolysaccharide

(LPS), C57BL/6 mice initially experienced a brief 

period of hypothermia. A febrile response then developed about 6 to 8 hours after injection, with a 

dramatic increase in the amount of time spent in 

non-REM sleep. This occurred relatively quickly, and

the suppression of REM sleep was finished within 

12 hours. In contrast, IL-6 knockout mice showed 

a significant hypothermic response. Temperatures

went down 5 to 6 degrees, then recovered, and were

back to baseline within 12 hours. Enhancement of

non-REM sleep of IL-6 knockout mice in response to

LPS was exactly 50 percent of the enhancement

observed in C57BL/6 mice, and suppression of REM

sleep was virtually identical to that of the C57BL/6. 

After administration of LPS, both strains, when

asleep, exhibited a reduction in EEG delta power—

the frequency band that is primarily manifest during

non-REM or slow-wave sleep. However, by 5 to 

6 hours after injection, the C57BL/6 mice were exhibiting slightly more power in the delta frequency

band, whereas the IL-6 knockouts remained reduced

in this measure. Focusing specifically on the one 

hour when the difference between the two strains 

was greatest, it was apparent that there was an

increase in this intensity measure in C57BL/6 and 

a reduction in the IL-6 knockout mice that was 

characteristic of all the frequencies analyzed in 

the study. The IL-6 knockout mice responded 

much differently to immune challenge than did 

the C57BL/6 mice, even though other aspects of

sleep/wake behavior were similar under nonchallenged conditions or in response to a relatively 

modest homeostatic challenge. These changes 

could be detected in the animals, both at the level 

of gross behavior and at the level of brain activity, 

as reflected in EEG patterns.

60 Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State 
Conclusion

As these studies demonstrate, CRH and the HPA 

axis are generally involved in the modulation of

arousal. Most pro-inflammatory cytokines that 

have been studied to date, at some point and 

under some conditions, will increase the amount 

of time animals spend in non-REM sleep. Interactions between many different neurotransmitters, 

but certainly between CRH and the HPA axis 

and cytokines, are of functional consequence to

behavioral outcome measures. Any stimulus that

alters the normal expression of these systems has 

the potential to alter sleep/wake behavior and 

contribute to excessive daytime sleepiness or 

disrupted nighttime sleep.

Discussion

Dr. Sternberg: Is there a difference in the males and

females in this case? Is there a critical age period?

Dr. Opp: There are definitely gender- and agerelated differences. We have not looked at female

IL-6 knockout mice. We have conducted some 

aging studies using the Fischer rat, which are 

in the process of being analyzed. We have not

looked at any gender differences.

Dr. López: When you gave the CRH antagonist, 

you saw an increase in IL-1, and you also said 

that the glucocorticoids decrease the expression 

of interleukins in these regions. Would you 

expect giving CRH to abolish the effect in 

non-REM sleep in these animals?

Dr. Opp: It is a question of timing. These two 

systems are inversely related to each other with

respect to their expression. We antagonized the 

system during the dark period when HPA axis 

activity is high and the message would normally 

be low for IL-1. By breaking that negative feedback, in addition, releasing that inhibitory tone, 

the message was increased. Had we done the same

manipulation 12 hours later, I am convinced we

would not have seen that result, because these 

systems must be antagonized at the appropriate 

time. If you increase the activity of the HPA axis 

system, then you will certainly affect cytokineor IL-1-mediated behaviors in the brain.

Cytokines–Neurotransmitter Interactions and the Regulation of Arousal State 61

S

leep is regulated, in part, by a brain biochemical

network. During the past 20 years, many components of this network have been identified 

and the specific links between a sleep regulatory 

substance and behavior have been characterized. 

This presentation focused on three of these sleep 

regulatory substances: growth hormone-releasing 

hormone (GHRH), interleukin-1-β (IL-1-β), and

tumor necrosis factor-α (TNF-α). The characterization of these substances as sleep regulatory substances grew out of an earlier literature which 

demonstrated that the transfer of cerebrospinal 

fluid from a sleep-deprived animal to a normal 

animal enhanced sleep in the recipient. Further 

characterization of the involvement of GHRH, 

IL-1, and TNF in sleep regulation followed, in 

part, a classic experimental paradigm developed 

in endocrinology—that of using pathology to 

identify physiological mechanisms. Thus, in one 

or more disease states GHRH, IL-1, and TNF 

are altered and those changes are associated with

sleep disturbances. It seems likely that the fatigue 

and sleepiness associated with chronic fatigue, 

regardless of etiology, are associated with changes 

in these molecules.

Growth Hormone-Releasing Hormone

Linkage exists between pituitary release of growth 

hormone and sleep. Takahashi in 1968 showed that

about 50 percent of daily growth hormone output 

in humans occurs in the first non-REM sleep period;

this solid finding in humans has now been extended 

to other animals. On the other hand, situations in

which plasma levels of growth hormone could be 

separated from sleep regulation were also known. 

In the mid-1980s, it was hypothesized that GHRH

could induce non-REM sleep and it can also induce

growth hormone release, but those mechanisms are

anatomically separate.

When GHRH was given to rabbits, the highest 

doses provided the longest effects in promoting 

non-REM sleep. Microinjecting into the intrapreoptic area of the hypothalamus induced these 

increases. There was no effect on temperature. 

These doses also induced increases in REM sleep.

When the animals’ pituitary glands were removed,

only the increases in non-REM sleep occurred, indicating that the effects on REM sleep are mediated 

by growth hormone while non-REM sleep effects 

of GHRH are mediated through GHRH itself.

Intrapreoptic injection of a peptide antagonist of

GHRH inhibited spontaneous sleep, suggesting 

that GHRH is involved in spontaneous sleep.

Feedback mechanisms related to internal GHRH 

and GH production involve somatostatin and 

insulin-like growth factor (IGF)-1, both of which 

are negative feedback signals. After administration 

of octreotide (a long-lasting somatostatin analog) 

or IGF-1, there is an inhibition of growth hormone

release and non-REM sleep, most likely because it 

is feeding back and turning off GHRH release.

GHRH release also can be inhibited in other 

ways, for example, with antibodies. 

Mechanisms Underlying the Central Effects of Cytokines 63

Mechanisms Underlying the Central Effects of Cytokines

James Krueger, Ph.D.
GHRH message production and release of GHRH

from the hypothalamus co-vary with non-REM 

sleep. This is corollary evidence only. During periods 

of sleep deprivation, synthesis of GHRH goes up 

and GHRH synthesis release is correlated with 

non-REM sleep.

In one experiment injecting GHRH, we used the 

lit/lit mouse, a model with a GHRH receptor deficiency caused by a single base mutation that results 

in a single amino acid substitution in the protein for

the growth hormone-releasing receptor. Called lit/lit

because they are little, these mice are small because

the GHRH receptors are nonfunctional; they do not

recognize GHRH and therefore do not release pituitary growth hormone. When the control animals

were given GHRH, their amount of sleep increased.

The lit/lit mice did not respond to GHRH and had

substantially less non-REM and less REM sleep than

the controls. With growth hormone therapy, lit/lit

mice started growing and their IGF-1 increased. NonREM sleep was unchanged but REM sleep returned

to normal, indicating that the effects of GHRH on

REM sleep are mediated via the growth hormone.

Cytokines

It has been known for some time that when a person is ill, growth hormone levels go up. At least 

15 years ago, studies determined that IL-1 stimulates growth hormones. In one rat study, 2.5 nanograms of IL-1 were injected, leading to increases 

in growth hormone. It was clear that the increases

were GHRH-mediated because animals pretreated with GHRH antibody and given IL-1 did not 

demonstrate similar increases in growth hormone. 

In simultaneous sleep experiments, non-REM sleep

increased in rats given IL-1. In animals pretreated

with GHRH antibodies, there was less spontaneous

sleep and virtually no response to IL-1, indicating 

that IL-1-induced non-REM sleep involves GHRH.

With current technological advances that afford 

closer looks at cellular mechanisms, we began to

examine the responses of cultured hypothalamic 

neurons to IL-1-β and GHRH to see if there was a

co-localization of the receptors on the same neurons.

Measuring cytosol calcium levels, intracellular calcium increased with IL-1; the same thing happened

when GHRH was administered. The cells are now

known to be receptive for both GHRH and IL-1;

there is a co-localization. These cells are also 

known to be GABA-nergic, which dovetails 

with the sleep literature.

Demonstrating a further relationship between IL-1

and GHRH, when IL-1 is given in vitro, it induces

production of the GHRH receptor. Not only do the

receptors co-localize in the same cells in the hypothalamus, IL-1 can induce GHRH receptor, although

it is not clear whether the animal is more susceptible

to GHRH after receiving IL-1. While it has been

shown that IL-1 can work to induce sleep via 

GHRH, it is not known if the reverse is true. 

In a study in our laboratory, we infected lit/lit and

control mice with influenza. The control had a normal response to influenza, sleeping more with somewhat flattened rhythms, but the lit/lit mice slept less,

with substantially less survivability. This suggests 

that the GHRH receptor is an integral part of the

response to influenza challenge, in terms of sleep 

and survivability. Administrating growth hormone 

did not rescue the animals, indicating a true GHRH

receptor-mediated event that is not GH dependent.

When IL-1 was administered to control and IL-1

receptor knockout mice, the responses of the knockout mice demonstrated that the receptor is involved 

in the sleep response to IL-1. 

IL-1 is related to sleep and it is in the brain. Examples

from the hypothalamus, hippocampus, and cortex

showed spontaneous levels of IL-1 in a regular diurnal

rhythm in all three areas of the brain. The message

levels were higher during the day, when the animals

were sleeping, than at night. In sleep-deprived animals, cytokine message levels went up in the four

areas of the brain measured: hippocampus, hypothalamus, brain stem, and cortex. Protein levels 

also increased. These effects were specific to IL-1-β.

These findings shed light on why, for

example, a lung disease such as influenza

induces brain symptoms even though the

disease is largely confined to the lungs.

An experiment by one of my graduate students indicated at least one mechanism by which cytokines 

signal the brain. In the context of an experiment 

testing how feeding affects sleep, rats were given 

a junk-food diet. They ate more than on a normal

diet and slept more, and the effects were shown to 

be IL-1 dependent. Animals were injected intraperitoneally with IL-1. The IL-1 that was signaling the

brain was probably produced peripherally. IL-1

induced its own messenger, a finding that has been

replicated in other work. Vagotomy on the animals

64 Mechanisms Underlying the Central Effects of Cytokines
did not affect IL-1 production in the liver because

nothing was blocked; there was still an increase 

in IL-1 messenger. In the brain stem, however, the

induction of IL-1-β was completely blocked. It is

known that the vagus nerve contains receptors for 

IL-1. IL-1 was injected and it bound to receptors 

on the vagal nerves; action potentials were elicited

and the action potentials made their way to the 

brain and were somehow translated into increased

messenger production for IL-1. This can be blocked

with a vagotomy. 

Cytokines are known to induce fatigue.

Whether this fatigue is the same as

what is seen with CFS is not known.

These findings shed light on why, for example, a lung

disease such as influenza induces brain symptoms

even though the disease is largely confined to the

lungs. Many of the brain symptoms occur before the

edema that accompanies influenza; these effects are

dose dependent and are not seen with higher doses,

which can get in the brain by other mechanisms. They

can be transported across the blood-brain barrier,

they can go through leaky areas, and they can induce

secondary molecules, such as prostaglandins, and 

then make their way through the blood-brain barrier.

The cytokines referred to in human studies are 

circulating cytokines, whereas in animal work 

central production of cytokines can be studied. 

This creates two bodies of evidence, one looking at 

circulating levels and the other looking at central 

levels; when they yield differing answers, it may 

be necessary to determine what the circulating

cytokines do. Considerable evidence points to the

ability of circulating cytokines to signal the brain

through a variety of mechanisms, including the 

vagus nerve. Cytokines are known to induce fatigue,

as is documented in some studies of humans; an

example is patients who report fatigue and sleeping

more when injected with IL-1. Whether this fatigue 

is the same as what is seen with CFS is not known. 

The biologic effect of cytokines is dose dependent.

Low doses tend to have positive results; for example,

low doses of TNF are neuroprotective against

ischemic damage to the brain and high doses do 

the opposite. Low doses of IL-1 and TNF promote

sleep; high doses do the opposite, due to feedback

mechanisms. Cytokine doses are extremely small, 

so these are potent substances.

Tumor Necrosis Factor

TNF messenger RNA and protein levels vary in 

phase with the sleep/wake cycle in a pattern that is

correlated but not proven to be causative. Injecting

TNF produced causative data. In sleep-deprived rats

there was an upregulation of TNF messenger RNA 

in the hypothalamus. Microinjection of TNF into 

the preoptic area led to increases in non-REM sleep

but had little effect on REM sleep. When an inhibitor was microinjected—in this case the TNF soluble

receptors, which increase in human plasma in times 

of sleep deprivation and are a normal component 

of cerebrospinal fluid in humans—spontaneous 

sleep was inhibited. This fits well with the sleep 

literature, which indicates that the preoptic area 

is used for sleep regulation.

There is some evidence that TNF is produced in

response to action potentials in neurons. Much 

of this data comes from researchers interested in 

kindling, a process of development of epilepsy in 

animal subjects. Increases in brain production of 

TNF are seen in the process. We have examined 

in vitro neurons after they have been treated with 

a glutamate stimulus. A dose-dependent increase 

in TNF production was seen, both in the media 

and in the cells.

Some data suggest that TNF is released as a function of its own use. Sleep is targeted to areas of the

brain depending on prior neuronal use; how much 

a person has used his or her brain depends on how

much the brain sleeps or its level of sleep intensity.

A hypothesis regarding sleep intensity is that the 

unilateral application of sleep regulatory substance

should induce EEG asymmetries. In earlier studies of

factor S, a sleep regulatory substance, high-amplitude

slow waves were seen that initially looked like an

artifact; however, sleep deprivation, which endogenously built up sleep regulatory substances, also

showed the high-amplitude slow waves. This provided 

a measure of intensity of sleep, and there is now a

large body of literature supporting this concept.

If TNF is put on the surface of the cortex just under

the dura, a difference between the two sides is evident: the amplitudes are higher on one side of the

brain. In time-dependent and frequency-dependent

fashion, low doses induce an increase in amplitude in

slow-wave activity. Higher doses induce larger effects

that are more persistent. These results mimic the consequences of sleep deprivation. When there is sleep

Mechanisms Underlying the Central Effects of Cytokines 65
rebound, if the sleep deprivation was short, the

rebound is usually confined to non-REM sleep 

with little effect on REM sleep.

Several laboratories have shown that TNF in the

brain signals through the AMPA receptors, and

AMPA receptors are needed for EEG synchronization. The downstream events of the cytokines 

IL-1, TNF, and GHRH have been well described.

Nitric oxide is a common downstream event 

for many of the substances that are known 

to affect sleep.

Studies of knockout mice in my laboratory determined spontaneous sleep in two different types 

of mice lacking either neural nitric oxide synthase

(nNOS) or inducible nitric oxide synthase (iNOS). 

The major finding was that if the animals lacked

nNOS, their non-REM sleep was normal and their

REM sleep was substantially reduced, especially 

during daylight hours. In contrast, if the animals

lacked iNOS, they had more REM sleep than normal and less non-REM sleep. These studies and a 

variety of others indicate that nitric oxide and its

enzymes that control synthesis, nitric oxide synthase, are involved as a downstream event, at least 

for effects on REM. That conclusion is generally

accepted, but the role of nNOS or iNOS in nonREM sleep is more controversial.

Theoretical Considerations

Thinking about biochemical sleep mechanisms 

leads to a new way of thinking about how the 

brain is organized to produce sleep and what 

sleep evolved to do. This knowledge is related to 

CFS because part of the brain can be asleep while 

another part of the brain is awake, which eventually might have implications for CFS treatment 

and understanding the syndrome.

A neuronal group theory of sleep function was 

published about 10 years ago. The following are 

the main tenets of that theory:

• Sleep is a fundamental property of groups 

of highly interconnected neurons, called 

neuronal groups. Other researchers have 

hypothesized that there are more than 

100,000 of these groups within the brain. 

An example of what these groups look like 

is the individual barrels of the sensory cortex 

of a rat, where about 10,000 neurons are 

organized around a single facial whisker, 

which receives afferent input and then 

sends signals to other parts of the brain.

• Homeostatic sleep mechanisms cannot be 

separated from sleep function. The molecules that are known to be involved in 

sleep regulation provide information 

about sleep function.

• Sleep function deals with neural connectivity. This is not to suggest that sleep serves 

a single function any more than the lungs 

serve a single function. Sleep probably 

evolved for a primordial function and, as 

it was evolving, other functions evolved 

with it. That primordial function deals 

with neural connectivity.

• The need for sleep is derived from the 

advantages of a flexible microcircuitry. 

Living organisms could have evolved 

as fixed, hard-wired computers or with 

flexible wiring of the brain; the advantages 

of flexible wiring are immense.

A discussion of sleep mechanisms expands upon 

these ideas. First, there is an activity-dependent 

production of sleep-regulatory substances. Neurons

produce substances, dependent upon how active 

those neurons are. The concept that neurons produce substances in response to changes in membrane potential across the extracellular membrane 

is not new, but researchers are now seeing that 

those changes lead to the production of sleepregulatory substances. One sleep-regulatory 

substance is nerve growth factor and another 

is brain-derived neurotropic factor. Both of these 

molecules are released from neurons as a function 

of neuronal activity. The release of other sleepregulatory substances is also dependent on past 

neuronal activity.

The activity-dependent, sleep regulatory substances 

act in autocrine, juxtacrine, and paracrine fashions 

to change the electrical properties of nearby neurons

and thereby alter input/output relationships. A large

body of literature demonstrates that many different

compounds, when applied onto a neuronal network,

will change the input/output relationships of that 

network. One of the better studies of interest to 

fever researchers is IL-1 put into hypothalamic 

networks; researchers then study the effects on the

hypothalamic neurons, including their sensitivity 

to temperature. IL-1 changes the sensitivity; for 

the same input, there is a different output.

66 Mechanisms Underlying the Central Effects of Cytokines
The altered input/output relationship for a neuronal group is, by definition, an altered state. For

example, where an environmental input gives an 

output that makes sense in terms of the environment this can be characterized as an awake state 

or a deterministic state. In contrast, if that input/

output relationship shifts, at some point the output 

will not make sense out of the environmental 

input (a chaotic state). 

Sleep is not only for neural connectivity,

but also because of it.

The activity-dependent sleep regulatory substances 

are also growth factors. They provide for the structural basis of synaptic efficacy and neural connectivity.

This is not controversial at all for some of the molecules known to be sleep regulatory substances, for

example, nerve growth factor (NGF), brain-derived

neurotrophic factor (BDNF), and nitric oxide. Others

(for example, IL-1 and TNF) are more controversial

in terms of their roles in brain connectivity but may

be less so as time goes on.

The altered input/output relationships provide 

stimulation for, and thereby preservation of, synapses not stimulated by the prior environmental

input. These alterations stimulate the synapses; 

therefore, the efficacy of transmission of action 

potentials or electrical signals through the synapses 

is enhanced. Expressed in plasticity modeling terms,

Hebbian processes dominate during waking while 

scaling processes characterize sleep.

A number of substances have been well characterized as sleep-regulatory substances and are 

known to be involved in some aspect of synaptic 

plasticity or neural connectivity. These include:

• Non-REMS: GHRH, TNF, IL-1, adenosine,

PGD2, NGF, BDNF

• REMS: VIP, PRL, NO, Ach

• W: CRH, hypocretin, NA 5-HT, Ach

These substances are characterized as Process S, 

one of two branches of a two-process model of 

sleep regulation developed by Borbély. Process S 

is a homeostatic process and consists of buildup 

of sleep-regulatory substances during wakefulness 

and dissipation during sleep. The other part of 

the model is a circadian process, Process C, 

which sets the levels at which sleep occurs 

and does not occur. 

Sleep-regulatory substances that have been demonstrated to have activity-dependent production are

NGF, BDNF, IL-1, TNF, nitric oxide, adenosine, 

and neural transmitters. For all of these substances, 

it is known that there is an activity-dependent production and release; this is how the brain can target

sleep to areas dependent on past activity.

A long list of sleep regulatory substances are 

implicated in synaptic plasticity: NGF, BDNF, IL-1,

NO, PRL, VIP, PACAP, adenosine, prostaglandins,

somatotropic axis, EGF, FGF, GDNF, NT3, NT4, 

IL-2, IL-6, IL-8, IL-18, IFN-α, TGF-β, PAF, and 

estrogen. Not all are well characterized as sleepregulatory substances, but all have been shown 

in at least one laboratory to affect sleep. Most 

of them promote sleep, but some actually inhibit

sleep, such as TGF-β. This reinforces the view 

that sleep has something to do with plasticity, 

since most of the substances that affect sleep 

also affect plasticity. 

Sleep is not only for neural connectivity, but also

because of it. The sleep need is derived from the 

flexible microcircuitry, its use-dependent rules, and

the necessity of preserving those synaptic networks

responsible for innate and learned memories. Some

experimental evidence suggests that sleep is involved

in neural connectivity. The bigger question about 

the need for sleep and where that need comes from 

is critically important, because the answer to this

question will provide insights into better clinical 

care in conditions such as CFS.

Mechanisms Underlying the Central Effects of Cytokines 67
In rat studies, we have determined that sleep loss 

and sleep gain affect the expression of molecules

linked to synaptic plasticity. Levels of mRNA after

sleep deprivation and excess sleep (triggered by

increased ambient temperature) were examined 

in three molecules. The first was BDNF, which is 

not only known to be involved in plasticity but is 

also a sleep-regulatory substance. The second was

activity-related cytoskeletal (ARC) protein, which 

is one of the better-characterized molecules within 

the plasticity field. Its messenger RNA is found 

in the dendrites and it is expressed as a function 

of local activation or local changes in excitatory 

post-synaptic potentials within the dendritic tree. 

This allows targeting not only an area of the brain, 

but also what is in a cell for induction of ARC 

message and translation of the message into protein. The third substance is matrix metalloproteinase 9 (MMP-9), also called gelatinase B. It is 

also involved in plasticity, although its involvement 

is, in one sense, the opposite of ARC: it digests the

extracellular matrix to make a new synapse.

In all of these compounds, the sleep effect is evident 

in the expression of their mRNAs. BDNF and ARC

increased with sleep loss whereas MMP-9 decreased.

When the animals slept more, mRNA went in the

opposite direction: BDNF and ARC decreased and

MMP-9 increased. 

Well-characterized plasticity molecules seem to be

affected by sleep. However, there are thousands of

molecules involved in plasticity and not every one 

of them will prove to be sleep sensitive. This is a 

complex field, and it will take many years to work

out the relationship between sleep and plasticity but

this is a beginning, and other researchers are beginning to direct their efforts to this area. Research on

NGF immunoreactivity by graduate students in our

laboratory tested the effects of sleep deprivation,

which alone resulted in increases in NGF immunoreactivity. The number of cells increased and the

amount within individual cells also increased, and

NGF distribution within the cell changed. The next

part of the experiment used the rat whisker cut

model, which is popular in the field of plasticity.

Researchers cut the whiskers on one side of the face,

which reduced afferent activity into the contralateral

somatosensory cortex because the whiskers did not

get stimulated as much. The whisker cut was then

combined with sleep deprivation. The brain on one

side, with intact whiskers, was relatively normal 

with appropriate input, but the side linked to the 

cut whiskers had much less input. 

On the intact side, sleep deprivation enhanced 

NGF immunoactivity. However, on the side that 

had reduced activity because of the cut whiskers,

instead of enhancing expression of NGF, sleep 

deprivation reduced its expression. This clearly

showed an interaction between sleep loss and 

the ongoing changes that occur within a neuronal

group. If the whiskers are cut on one side of the 

face, within 24 hours the neurons will begin to 

reorganize their connectivity on the opposite side 

of the animal. They will start to connect with 

other neurons from other neuronal groups or 

other barrels that are involved in afferent input 

from different (uncut) whiskers. Sleep appeared 

to affect that reorganization, or at least affect 

molecules involved in plasticity, in a different 

way than if the whiskers were intact.

Theoretical constructs currently under consideration and testing will, over time, tell a great deal 

about how the brain is organized to produce sleep,

what sleep is about, and provide new avenues to

change how the brain operates, allowing scientists 

to target parts of the brain during wakefulness or

during sleep.

68 Mechanisms Underlying the Central Effects of Cytokines
Will Understanding Central Mechanisms Enhance the Search for the Causes, Consequences, and Treatment of CFS? 69

Session Four: Will Understanding Central Mechanisms Enhance 

the Search for the Causes, Consequences, and Treatment of CFS?

Chair: Dedra Buchwald, M.D.

This session of the conference holds implications for designing studies and answering questions 

about the nature and causes of chronic fatigue syndrome, as well as the existence of neuroimmune 

modulators or influences. New methodologies include innovative study designs, such as twin and 

family studies, studies of other disorders, use of new technologies or new applications of existing technologies, and thinking about CFS in a different way or using a different approach. For example, rather 

than investigating symptoms or problems that CFS patients develop, perhaps questions should be asked 

about the symptoms and problems not developed by CFS patients and how that knowledge might inform 

the field about the pathophysiology and mechanisms behind CFS.

Amultiplicity of symptoms characterize chronic

fatigue syndrome (CFS). Acute onset and persistence of fatigue is the defining symptom, but

other symptoms are part of the CFS diagnosis, including (in order of frequency) sleep disturbances, muscle

weakness, difficulty concentrating, worsening with

stress, joint and muscle pain, difficulties with attention and concentration, weight gain, increased need

for sleep, and headaches. The causes of CFS are

unknown, but its manifestations are multiple and

include both body (such as muscle fatigue and pain)

and brain (central nervous system) symptoms. More

women than men are diagnosed with CFS. In a manner similar to other physical illnesses, such as chronic

pain or other physical disabilities, its permanence 

and continuous impact on the life of those affected

can induce complicating syndromes, such as major

depression, itself an illness typically induced by 

emotional and physical stress. 

Other idiopathic forms of persistent pain which 

complicate CFS, such as fibromyalgia syndrome, 

temporomandibular joint pain, and major depression, are also more frequently diagnosed in women 

of reproductive age. CFS is a more common diagnosis in monozygotic than in dizygotic twins, suggesting that some vulnerability for the initiation or

permanence of CFS may be due to genetic influences.

Genetic, gender-related, and stress-related factors,

therefore, should be examined for their contribution

to the pathophysiology and manifestations of CFS.

(Stress is defined broadly here as insults—physical,

such as chronic illness or pain, or emotional, such 

as severe life events—that destabilize the homeostasis of the organism.) 

We are therefore describing a research avenue that

necessitates a systems-level understanding of this illness and an illness that falls into complex pathologies

in which genetic, psychophysical, and environmental

factors interact. In that regard, CFS is not unique,

and it joins syndromes as diverse and as poorly

understood as persistent muscular pain, dysautonomias, depression, and irritable bowel syndrome. This

perspective has relevance for the types of approaches

needed to unravel the multiple manifestations of CFS.

Complex illnesses are not characterized by a single

phenomenon that leads to an illness process; they are

caused by interactions between biological or genetic

vulnerabilities and other factors, such as infections,

injury, and environmental factors that may foster 

the transition from vulnerability to a pathological

state. For example, major depression, another illness

of complex etiology, can develop in vulnerable individuals as a result of interactions among genetic vulnerability and factors, such as life events, stressors,

infections, injuries, or persistent pain, and it is more

frequently diagnosed in women. Gender, hormones,

or both may then induce additionally increased 

predisposition toward certain complex illnesses in

which a gender predominance is observed, such 

as in CFS or persistent pain syndromes.

We are therefore describing a research

avenue that necessitates a systems-level

understanding of this illness and an illness that falls into complex pathologies

in which genetic, psychophysical, and

environmental factors interact.

My discussion centers on possible perpetuating 

mechanisms that aggravate the course of CFS and

may induce a vicious circle of vulnerability to dysregulation to further worsening, focusing on the 

CNS, a locus of manifestation of a number of CFS

symptoms. I review the literature on central nervous

system findings in CFS, and recent studies from our

and other laboratories that exemplify neurobiological models of interaction among genes, gender, 

stress, pain, and affective regulation as possible

avenues for discovery in CFS.

Brain Stress–Response Circuitry in the Regulation of Physical and Affective States 71

Brain Stress–Response Circuitry in the Regulation of Physical 

and Affective States

Jon-Kar Zubieta, M.D., Ph.D.
Initial studies with magnetic resonance imaging 

(MRI) in patients suffering from CFS have shown

areas of increased signal intensity, typically interpreted as reflecting neuronal changes due to edema or

demyelination.1,2 Changes in the blood flow and 

the glucose metabolism of various brain regions, 

primarily frontal and temporal, have also been 

reported during baseline, neutral states in CFS.3-6

However, these findings have not been replicated in

other studies, notably one comparing monozygotic

twins discordant for the presence of CFS, in which

genetically related variations in brain metabolism 

are controlled for in the design.7 In addition, none of

the positive findings with these baseline measurements

have demonstrated changes during resting states that

are defining or specific for CFS. Measures of regional

cerebral blood flow, metabolism and, more recently,

functional MRI responses to various stimuli are related to synaptic activity during the study conditions.

Baseline measurements most likely reflect the CNS

representation of symptoms of the illness, which in

isolation are again not unique for CFS. 

The question then remains as to what circuits and

mechanisms in the brain may participate in the interaction between possible genetic vulnerabilities, stress,

and gender to contribute to the manifestations of CFS.

None of us has the answer to that question. However,

for the purposes of exploring new avenues of investigation, I will draw some parallels from recently

acquired data in experimentally induced sustained

pain using imaging techniques to more specifically

examine the neurochemical systems involved in its 

regulation in humans. We utilized positron emission

tomography (PET) with radiotracers that specifically

label receptor systems, affording an additional level 

of neurochemical specificity that cannot be obtained

with measures of metabolic or synaptic activity.

As experimental pain goes from acute (lasting from a

few seconds to a few minutes) to more sustained (lasting more than 5 or 10 minutes), its sensory qualities,

which define location, perceptual quality, and intensity, remain constant; its affective qualities, which relate

to how unpleasant and emotionally burdensome it

becomes, sharply increase.8 Pain is then transformed

from an organism’s warning signal to a stressor that

threatens well-being and activates the production of

stress hormones, such as cortisol. It is therefore not

surprising that painful and noxious stimuli have frequently been utilized in animal models as a model of

stress, in a manner similar to other stressors such as

those posed by environmentally adverse events.9-12

The question then remains as to what

circuits and mechanisms in the brain

may participate in the interaction

between possible genetic vulnerabilities,

stress, and gender to contribute to the

manifestations of CFS.

What happens in human subjects as pain becomes

more sustained and therefore becomes a stressor?

Aside from the initial transmission of pain signals 

to brain regions involved in its representation,13

sustained pain activates mechanisms that attempt 

to suppress it, so some degree of homeostasis can be 

re-established. We have studied the latter mechanisms

directly in humans with PET and radiotracers labeling receptors involved in the suppression of stress 

and pain. One of these receptors is the μ-opioid 

receptor. These receptors mediate some of the actions 

of endogenous opioids—peptide neurotransmitters

that are released in response to various stressors,

including pain and inflammatory processes. The 

μ-opioid receptors are also the targets of opiate 

medications used to reduce acute or chronic pain.

We have utilized a model of sustained muscular 

pain induced by the introduction of small amounts 

of hypertonic saline into the jaw muscle to temporarily induce temporomandibular pain, a frequently

observed complicating symptom in CFS by itself and

together with fibromyalgia. The pain is maintained

constant at low levels: 40 units of intensity as graded

from 0 (no pain) to 100 (most pain imaginable) as

rated by the subjects. Obtained every 15 seconds 

with the aid of an electronic visual analog scale, 

pain ratings are fed back into a computer controller that modifies the infusion rate of the hypertonic 

saline infusion, so that pain is maintained as constant as possible for the duration of the challenge

(typically 20 to 30 minutes). This stimulus activates

the hypothalamic-pituitary-adrenal hormonal stress

responses, inducing increases in the production of

ACTH and cortisol.14 Simultaneously, subjects were

scanned with PET and the radiotracer [11C]carfentanil, which selectively labels μ-opioid receptors, 

during pain and during a nonpainful challenge 

(isotonic saline) infused in the same manner as 

the noxious stimulus.

In an initial series of studies in 20 healthy volunteers

(14 men and 6 women, 20 to 30 years of age), we

demonstrated that the pain stimulus was associated

72 Brain Stress–Response Circuitry in the Regulation of Physical and Affective States
with activation of endogenous opioid neurotransmission, observed experimentally as reductions in the

binding measure obtained with PET, [11C]carfentanil,

and kinetic quantification models. As the endogenous

neurotransmitter is activated, it competes with the

radiolabeled tracer; less μ-opioid receptors are available for the radiotracer to bind, hence the reductions

in the in vivo binding measure. Significant activation

of μ-opioid receptor-mediated neurotransmission was

observed in a number of brain regions, including the

prefrontal, anterior cingulate, and insular cortices;

thalamus, both anterior and lateral; hypothalamus;

and in the ventral basal ganglia (nucleus accumbens

and ventral pallidum), amygdala, and periaqueductal gray.15 Retrospectively, and given the widespread 

distribution of μ-opioid receptors in the human brain,

the large number of regions involved in these responses seem reasonable, since pain is a complex experience; however, this result had not been observed

previously in animal models. The regions involved 

are associated with complex processes, including

attention and cognition-emotion integration (prefrontal cortex, anterior cingulate); bodily sensory 

perception and regulation (thalamus, insular cortex); hormonal responses (both stress related, such 

as ACTH production, and reproductive, hypothalamus); reward and salience evaluation (nucleus accumbens, ventral pallidum); assignment and regulation 

of emotional valence and stimulus intensity (amygdala); and pain control (periaqueductal gray). 

These results emphasized the important role of the

CNS in the perception and regulation of stressful

stimuli (in this case sustained pain stimuli) and 

how a neurotransmitter system, the endogenous 

opioid, and μ-opioid receptors, thought to be primarily involved in analgesia, also affect regions

involved in various elements of the stress response,

including higher order, attentional, and cognitive

functions. Perhaps more importantly, we observed 

a wide range of interindividual variations in baseline binding, as well as in the capacity to activate 

μ-opioid receptor-mediated neurotransmission, 

even though the pain model was controlled for 

intensity. The magnitude of activation of μ-opioid

receptors, calculated as the percent reduction in 

binding from control to pain scans, was further 

correlated with ratings of the sensory quality of 

the pain, its affective ratings, and the negative 

affective state induced by the noxious stimulus, 

albeit in distinct neuroanatomical localizations.15-16

In other words, the capacity to suppress various 

elements of the pain-stress experience was highly 

variable among individuals. Subsequent work was

then oriented toward understanding the sources of

this interindividual variability.

Pain stimulus was associated 

with activation of endogenous 

opioid neurotransmission.

We also examined whether men and women differed

in their capacity to activate this pain/stress suppressive neurotransmitter system.16 The gonadal steroid

status in the women was controlled by performing 

the studies in the early follicular phase of the menstrual cycle, when estradiol and progesterone are 

lowest. Binding measures were obtained under nopain and pain conditions in samples of 14 each,

healthy young (20 to 30 years of age) men and

women. Significant differences in the magnitude 

of activation of the endogenous opioid system and 

μ-opioid receptors were observed. Consistently, men

activated μ-opioid neurotransmission more efficiently

than women did, reaching statistical significance in

the thalamus, nucleus accumbens, and ventral pallidum and amygdala. This was associated with a 

more efficient suppression of the ratings of pain in

terms of its sensory qualities (nucleus accumbens,

amygdala), affective quality of the pain (anterior 

thalamus), and the negative affective state induced 

by the challenge (ventral pallidum). One more observation arising from these results was that, in women,

substantial interindividual variation was still observed

that was not related to plasma levels of estradiol or

progesterone, with 4 out of 14 women showing

responses that were more similar to those of men. 

We have further studied these variations with two 

different approaches: by varying the plasma levels 

of estradiol and progesterone (work currently in

progress) and by examining genetic variations 

that affect some of the circuitry involved.

In an initial approach to examine the contribution 

of genetic polymorphisms to the regulation of pain

stress, we focused on a common genotype variant

affecting the function of the enzyme catecholamineortho-methyl-transferase (COMT).17 Substitution 

of valine (val) by methionine (met) at codon 158 of

the COMT gene induces a reduction in the activity 

of the enzyme. This single nucleotide polymorphism 

is codominant, meaning that individuals with two

copies of the met allele, approximately 20 percent 

of the population,18 have the lowest COMT function,

those with one of each have intermediate function

Brain Stress–Response Circuitry in the Regulation of Physical and Affective States 73
(about 50 percent of the population), and those with

two copies of the val allele have the highest function

(about 30 percent of individuals). 

Our interest in the COMT enzyme arose from its 

role in the metabolization of dopamine and norepinephrine, both neurotransmitter systems involved 

in the regulation of stress and responses to salient

stimuli. Dopamine is an abundant neurotransmitter 

in some areas in which large interindividual variations in the response of the opioid system were

observed, such as the ventral basal ganglia (nucleus

accumbens and ventral pallidum), as well as in the

rostral anterior prefrontal cortex, anterior cingulate, and amygdala. At the level of the basal ganglia,

studies in animal models had shown that the persistent activation of dopaminergic neurotransmission 

(a situation presumably similar to that of a lowfunction COMT enzyme, with lower capacity to 

inactivate dopamine) reduced the neuronal levels 

of endogenous opioids and induced compensatory

increases in baseline μ-opioid receptor binding. 

We then tested whether variations in the function 

of COMT due to this polymorphism would be 

associated with variations in the human capacity 

to suppress the pain–stress experience through the

activation of endogenous opioid neurotransmission 

on μ-opioid receptors. Conducted 

in 29 healthy men and women, 

this study demonstrated that 

individuals with the lowest 

COMT function (met/met 

homozygous) had the lowest 

capacity to activate μ-opioid 

receptor-mediated neurotransmission, albeit they had the 

highest number of μ-opioid 

receptors; the latter finding is 

consistent with upregulatory 

changes in the concentration of 

the receptors in the context of 

less efficient release of endogenous opioids. Heterozygous 

individuals demonstrated 

intermediate responses of the 

system and intermediate binding 

levels, and val/val homozygotes 

had the highest capacity to 

activate μ-opioid neurotransmission and the lowest level 

of receptors. These varying 

capacities to activate μ-opioid neurotransmission 

were further correlated with the capacity to suppress

sensory, affective ratings of pain and the negative

internal affective state induced by the stressor.16

What are these results teaching us about CFS and

some of its associated symptoms, such as chronic 

pain, attention and concentration difficulties, difficulties in tolerating stress, and mood changes?

Behavioral responses to a sustained stressor—in 

this case pain, but in the case of CFS maybe a persistent infectious process and changes in peripheral

immunological factors—are regulated at the level 

of CNS neurochemical systems. These responses 

are interindividually variable, with both gender 

and genetic factors contributing to their short-term

regulation. These variations may then contribute to 

the vulnerability or resiliency for development of

pathological states, and the propensity to become 

further dysregulated over time. The regulation of

stress, pain, and possibly other illness states involves

brain regions also implicated in cognitive, emotional,

and reward functions, which may then dysregulate 

as the injury or stressor progresses to a more persistent illness state. In this regard, alterations in opioid

and dopamine receptor binding have been shown in

chronic inflammatory and pain conditions.19,20

74 Brain Stress–Response Circuitry in the Regulation of Physical and Affective States

Correlations between COMT val158met genotype and μ-opioid system activation in

response to sustained pain—ventral pallidum and amygdala.

Association between COMT activity conferred by met158val genotypes and μ-opioid

system activation in response to the pain stressor. Shown are the mean ± S.D. values

for the percent change in the magnitude of μ-opioid system activation in the ventral

pallidum ipsilateral to the painful challenge and the contralateral amygdala (with

some contribution of the adjacent anterior temporal cortex).
As a research agenda for CFS is developed, studies should be considered that address not only 

the immediate causes of CFS, but also the CNS 

mechanisms that become dysregulated during its 

persistence. Such mechanisms offer insight into the 

complex symptomatology of this illness and they 

also provide treatment targets for the symptoms.

Alterations in opioid and dopamine

receptor binding have been shown 

in chronic inflammatory and 

pain conditions.

Discussion

Dr. Goldstein: Regarding the COMT polymorphism,

biochemicals called catechol estrogens are substrates

for COMT. It is possible that the link between pain

perception and the COMT polymorphism may be

independent of catecholamine metabolism, but also

may be associated with the relative amount of available catechol estrogen. Most catecholamine metabolism takes place in the cells where it is produced.

COMT is not expressed in most central neurons, 

and it does not play a major role in the inactivation of dopamine or norepinephrine in the brain.

Dr. Zubieta: Regarding the comment of COMT

expression in central neurons, that is actually not 

the case. Effects of COMT polymorphisms have 

been shown on fMRI responses to cognitive stimuli,

and variations in COMT activity have been linked 

to dopamine release in animal models, showing 

some sex differences. Animal models and humans 

also differ in terms of the contribution of COMT 

to dopamine metabolism. While in animal models

COMT appears to be more involved in metabolizing dopamine and norepinephrine in cortical regions,

in humans it appears to be strongly involved also in

basal ganglia. There are some data in animal models

on how the blockade or manipulation of COMT

activity is associated with the release of monoamines 

in different areas of the brain. I am not certain

whether that is related to catechol estrogen, but

COMT is involved in metabolizing catecholamines 

in the CNS.

Dr. Goldstein: Our lab has the world’s most sensitive

assay for measuring metanephrines, the direct product

of COMT. It has never been done, as far as I know,

but if you think that COMT polymorphisms are 

altering catecholamine metabolism in a generalized

way, then there is a direct testable hypothesis in 

terms of plasma levels of metanephrines.

Dr. Pocinki: I would like to suggest going back to 

an old methodology: physical examination. In seeing

CFS patients over the years, and especially in the 

past year, I have been struck by the fact that all of 

the several hundred CFS patients have hypermobile

joints. We know these individuals are predisposed to

fibromyalgia and to tearing of periarticular muscles

because of the stress on their joints. They are predisposed to exactly the type of muscle pain and joint

pain without swelling or redness that is seen in CFS.

Joint hypermobility is a sign of diffusely increased tissue elasticity. The patients’ major problem is venous

distension—their blood vessels are too stretchy, so

they have pooling of blood and orthostatic intolerance. To compensate for their impaired circulation,

these individuals produce more catecholamine. 

These are the patients we saw in the Tahoe area 

who gave rise to the moniker “yuppie flu.” They 

are the high-energy, always on the go, marathonrunning, over-achieving people who run on adrenaline. When they try to go to sleep, they typically lie

there for an hour waiting to fall asleep. When these

people who have been running on adrenaline for

years suddenly experience an infectious, environmental, or emotional insult, they lose their compensation. They stop making extra catecholamine.

They describe exactly what our patients describe:

someone has pulled the plug and drained out all 

their energy. They develop fatigue and problems 

with cognitive function. If they try to exercise, 

they rob their vital organs of even more circulation and they become exhausted.

Question: Is there any evidence that COMT inhibitors

modulate pain perception?

Dr. Zubieta: We are beginning to study that now and

will know more in about 6 months.

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76 Brain Stress–Response Circuitry in the Regulation of Physical and Affective States
Cognitive aging is a plausible model for

fibromyalgia because fibromyalgia patients

have substantial memory and cognitive complaints. Normal adults have reliable memory function

and have particular sensitivity in the hippocampal

and frontal lobe systems. Some important neurochemical pathways, primarily the HPA axis, are disturbed

in fibromyalgia patients and are similarly disturbed 

in older adults. A neurochemical mechanism exists

that could mediate cognitive complaints. Believing

they had identified a plausible mechanism to account

for some of the cognitive complaints of fibromyalgia

patients, we developed a study that hypothesized that

fibromyalgia patients might have the cognitive function of adults 20 to 30 years older. Data collected on

cognitive aging included three measures of speed of

processing (how fast individuals process information)

and four measures of working memory (how much

information individuals can hold in their memory 

and manipulate in consciousness at any given time).

Both are measures of long-term memory in which

individuals are provided with lists of words or symbols and are asked to remember and recall them 

later. The measures are a proxy for word knowledge or vocabulary measures.

On reviewing our findings, we identified reliable

declines across the life span in processing capacity

abilities and in many modalities and domains.

Notably, the data showed nothing remarkable about

turning 60, 70, 50, or 30 years old. Beginning in the

20s, slow regular declines are seen across the life

span. (Olympic athletes 30 and 40 years old are like

20-year-olds.) The brain is part of the body and, like

every other body part, it ages gradually and almost

imperceptibly. However, with age comes wisdom;

individuals continue to accrue knowledge and expertise as they age. In addition, there is little evidence 

that as people age they become less effective, for

example, in their jobs. Age-related changes may be

observable only in occupations that involve heavy,

constant processing demands, such as air traffic control.

How are fibromyalgia patients different from agematched controls in their cognitive function? A quick

review of the literature elicited few studies on the

topic, and most were underpowered. All of the existing studies, even those that concluded that there was

no difference, showed that the fibromyalgia patients

consistently performed more poorly than the controls,

although not significantly so. Subject matching was

poor, and data were insufficient to suggest differences.

We recruited three groups of subjects and investigated their speed of processing, capacity, long-term

memory abilities, and category fluency. Subjects 

were screened for depression and were excluded 

if they had anything more serious than mild depression. Drugs that could affect memory function were

washed out for 2 weeks. The study included 23 subjects in each condition and 22 older controls; the

mean age of the fibromyalgia group was 47 and the

mean age of the older controls was 66. Education

was matched precisely among the groups. There 

were no systematic differences in the samples.

Subjects were always tested in triplicate, so that 

once a fibromyalgia patient was found, the research

team searched until it found the perfect control.

Cognitive aging is a plausible model 

for fibromyalgia because fibromyalgia

patients have substantial memory 

and cognitive complaints.

A score of 19 indicates mild depression on the Beck

scale; a score of 15 indicates mild depression on the

geriatric depression scale. The fibromyalgia patients

in the study were slightly more depressed than the

age-matched and older controls, but their scores fell

below mild depression. They had mildly negative

affect but were not depressed. The fibromyalgia

patients self-reported more pain than the older 

controls or the age-matched controls.

The Cognitive Neuroscience of Fibromyalgia 77

The Cognitive Neuroscience of Fibromyalgia

Denise Park, Ph.D.
To measure speed of processing, subjects were shown

pairs of symbols and were asked to answer as rapidly

as possible whether the two symbols were the same 

or different. The number of items an individual can

complete in 2 minutes is an extraordinarily sensitive

measure of how rapidly he or she processes information; it predicts variance on many cognitive tasks and

is one of the most powerful measures of cognitive

function. Fibromyalgia patients performed as well as

the age-matched controls, but the elderly adults performed more poorly than the young adults, as expected. The mean age of the young adult subjects was 48,

so the group did not include extraordinarily young

people, such as college students. The fibromyalgia

patients performed exactly like the younger adults.

Next, we measured working memory. For example, 

in one task, subjects were asked to listen to a sentence

and to process, store, and recall information from the

sentence. The researchers noted how many consecutive questions the subjects could answer without 

making an error. This difficult task represents an

accurate measure of available processing capacity. 

On the measures of working memory, the fibromyalgia patients performed like older adults. Although 

the fibromyalgia patients performed as well as the

age-matched controls in terms of speed of processing, they were significantly poorer and more like 

the older adults than the age-matched controls in

terms of working memory capacity.

We then measured long-term memory capacity by 

giving the subjects lists of words to remember. The

fibromyalgia patients performed like older adults and

both the fibromyalgia patients and older adults performed more poorly than the age-matched controls.

As a measure of verbal fluency, the subjects retrieved

from memory in 1 to 2 minutes as many words as

they could that began with a particular letter. This

task is age-sensitive; the ability to perform the task

declines with age. The fibromyalgia patients performed similarly to the older adults, and both groups

performed more poorly than the younger adults.

The fibromyalgia patients showed normal speed of

processing, similar to age-matched controls; however,

they performed significantly worse than age-matched

controls and similarly to older adults on measures 

of working memory, verbal fluency, and long-term

memory. The researchers also measured memory complaints, or meta memory, and found that fibromyalgia

patients complained more about their memory than

did other groups. The study suggests that fibromyalgia patients’ memory complaints reflect a reality 

that their memory is age inappropriate, rather than 

a complaint bias. We also tried to correlate pain,

depression, and anxiety with all of the memory 

measures; the only area that correlated was pain. 

Self-reports of pain correlated with memory function, but depression and anxiety did not.

The fibromyalgia patients showed 

normal speed of processing, similar to

age-matched controls; however, they

performed significantly worse than agematched controls and similarly to older

adults on measures of working memory,

verbal fluency, and long-term memory.

Functional imaging is the ability to look in the brain

at what components are being activated as a function

of cognitive tasks. We developed a functional imaging

technique to study fMRI and fibromyalgia in older

patients. In an almost completed study, young adults

and old adults were given a verbal working memory

task and a PET scan. During the task, both young

and old adults showed reliable activations in the left

frontal cortex in the left hemisphere of the brain. At

the top of the brain, good left hemisphere function

occurred in both the young and old adults, but in the

old adults, recruitment of the homologous areas and

additional frontal regions also was seen. This finding

emerges frequently in other studies: to perform a cognitive task, older adults recruit more of the brain in

the frontal area, typically the homologous regions,

than do young adults. Fibromyalgia patients showed

cognitive function that is reminiscent of an older

adult, but it was unknown whether they would show

neural activations similar to those of an older adult. 

To date, the data are based on 12 fibromyalgia

patients and nine healthy controls, but we plan to

include 15 fibromyalgia patients in our study. The

subjects are matched carefully, and anything that

could affect neural function, such as drugs, is washed

out. The subjects are scanned on a 3T magnet at the

University of Michigan using a spiral pulse sequence

and then are given a working memory task: they see

four letters on a visual display—such as S, B, G, and

Q—and they are asked to quickly alphabetize the 

letters mentally while their brains are scanned. A 

10-second slide allows their brains to come back to 

a resting state; it allows the hemodynamic response,

78 The Cognitive Neuroscience of Fibromyalgia
which is captured in fMRI, to return to baseline. 

We then observe what happens in the subjects’ 

brains at different stages of the task and see the 

different parts of the brain that come into play.

Although the time-course data are not yet in, data

have been collected on the parts of the brain that

were activated in the aggregate across the trial.

In the maintenance condition, subjects are shown 

four letters in alphabetical order and are asked to

hold them in memory for 3 seconds, then they are

shown a letter and asked if it is in the correct position. What is happening in these 3 seconds in the

maintenance condition compared to the alphabetizing condition, in fibromyalgia versus control patients? 

We conducted trials with three letters and with four

letters to see whether difficulty made a difference to

fibromyalgia patients. There was little difference in

activation between the three-letter and four-letter trials. Because brains are somewhat more active while

alphabetizing than while maintaining, subtracting 

the maintenance image from the alphabetizing image

leaves the residual activation of alphabetizing. The

tasks for the study were designed not to be overly

demanding, and the fibromyalgia patients and agematched controls were given the same tasks to perform so that any differences in brain activation could

not be attributed to differences in performance or to

errors. This study resulted in equivalent performance

between the fibromyalgia subjects and the control

subjects; therefore, differences in neural activations

between the groups cannot be attributed to differences in accuracy or to time on task. 

It is likely that certain tasks are more

demanding for fibromyalgia patients

than for control subjects, so fibromyalgia patients engage more of the 

brain when undertaking those tasks.

Images of the fibromyalgia patients’ brains in which

the maintenance data were subtracted from the alphabetizing data included different views of the same

activation from the right, top, and back of the head.

There was bilateral activation in the midline medial

frontal gyrus, with parietal activations in an area 

used for storage—the residual activation left while 

the subject is alphabetizing. Areas implicated in planning and storage showed enhanced activation in the

fibromyalgia patients during the alphabetizing task.

Similarly, a frontal area was activated in the left 

hemisphere—the analog to Broca’s area, which is

where language is processed in the left hemisphere.

Activation in the right hemisphere was also seen 

during the alphabetizing task, in areas involved in

rehearsal, in language, and in reasoning, providing

evidence of bilaterality. We believe that we observed

two-sided recruitment in both older adults and fibromyalgia patients during the alphabetizing condition,

although additional images are needed to confirm this.

Control subjects appeared to have adequate capacity

to perform the alphabetizing task, and little difference was observed in any parts of their brains when

alphabetizing was subtracted from maintenance.

Apparently, the alphabetizing task was less difficult

for individuals with a lot of capacity, and therefore

the fibromyalgia brains looked quite different from

the control brains.

The researchers also subtracted the brains of the 

control subjects from the brains of the fibromyalgia

patients, by stretching and moving the images slightly

so they are in the same anatomical space and look

anatomically identical. The fibromyalgia patients

appear to show more planning and more need to 

prepare before responding. The significance of the

medial frontal area, which is associated with eye

movements and visual reflexes, is unknown in

fibromyalgia. Activation was noted in the left thalamus, which is a gating area for pain and the site in

which most information that reaches the cerebral 

cortex is processed. The right caudate is a central 

area responsible for preparation and selection of

motor and emotional responses and formulation 

of strategies. The right inferior temporal gyrus and

the medial temporal areas, which are involved in

memory, were also evident on the scans. We will be

recruiting more subjects and performing time-course

analyses, which may reveal much more dramatic 

differences and which may provide a fuller picture 

of brain activity differences between the groups.

It is possible to subtract the fibromyalgia patients’

data from the control subjects’ data. In all slices 

of the brain, no significant activations in any slice 

or area of the brain were seen. The fibromyalgia

patients showed more neural activation when using

their working memory than did age-matched controls,

with the primary areas being pre-motor areas (planning areas), thalamus (gating of pain), and caudate

(strategizing and selecting emotional and motor

responses). Some bilaterality was seen in the analyses

in the frontal areas, reminiscent of aging. It appeared

The Cognitive Neuroscience of Fibromyalgia 79
that fibromyalgia patients need to activate more 

brain structures to alphabetize, and functional or

structural systematic differences were encountered 

in the fibromyalgia patients.

Do fibromyalgia patients use different strategies

because they are compensating, or have their brains

been rewired so that functions have become structurally different? We believe the latter interpretation

to be correct. It is likely that certain tasks are more

demanding for fibromyalgia patients than for control subjects, so fibromyalgia patients engage more 

of the brain when undertaking those tasks. 

It may be fruitful to compare fibromyalgia patients

with older adults in a scanner and to collect data 

on brain volume as well as structure (e.g., size of 

different structures and amounts of neural tissue 

they contain). If fibromyalgia patients chronically

dump large amounts of cortisol into their brains 

due to HPA dysfunction, it is plausible that such

actions damage the hippocampus in a systematic 

way and result in decreased hippocampal volume, 

as in older adults. Such a decrease would not be 

associated with activation but rather with amounts 

of neural tissue (i.e., how many voxels comprise 

the hippocampus in a fibromyalgia patient versus 

an age-matched control). 

This area of research is an interesting and important

frontier for understanding cognitive dysfunction in

fibromyalgia patients. Additional research is needed

on long-term memory and vocabulary issues in

fibromyalgia patients, as well as on the interface of

emotion and cognition. Research is likely to reveal

more dramatic responses to emotional stimuli in

fibromyalgia patients, a promising research arena.

Discussion

Dr. White: I was particularly interested in the 

findings using fMRI that patients with fibromyalgia

required increased activation of their brains for particular tasks. Were you able to measure the differential effect of the effort of performing different tasks,

such as information processing versus memory? 

How much do you think the sense of effort affected

the final results?

Dr. Park: The brain activation reflects that the

fibromyalgia patients “work harder,” using more of

their brains. Brain activation is the purest possible

measure of effort, particularly in the frontal areas.

There are other areas of the brain that one would 

not think reflect effort. The parietal areas are storage

areas, and the data suggest that fibromyalgia patients

have to engage more parietal areas to store information, again suggestive of diminished capacity and

increased effort.

Dr. Buchwald: You mentioned that you controlled 

for education, gender, depression, and other things. 

I did not notice whether you controlled for sleep.

Both older people and fibromyalgia patients have

poor sleep, and sleep is known to affect cognition.

Dr. Park: In the earlier study, we gave subjects

Actigraph watches. We measured sleep quality in 

the fibromyalgia patients, the older adults, and 

the age-matched controls. We did not find any 

systematic differences; we did not find that sleep 

quality correlated with cognition.

Question: We obtained similar results in a similar

study of CFS patients. We do not know whether 

neural activation drives cognition, although we

assume it does. Some data suggest that blood flow 

is lower in patients with CFS and fibromyalgia. 

The next generation of neuroimaging studies could

examine absolute blood flow, in order to connect

brain activity with other systems that may be 

dysregulated in CFS patients.

Dr. Park: It is possible that different hemodynamic

responses exist due to differentials in blood flow. We

can assess that, because we have data on individual

hemodynamic response functions, independent of the

functional imaging data. We can examine the extent

of normal function in this group of subjects.

80 The Cognitive Neuroscience of Fibromyalgia
The methodological significance and complexities of sex and gender can be demonstrated

using the model of irritable bowel syndrome

(IBS). Gender differences exist in a number of common functional disorders, including fibromyalgia,

migraine headaches, IBS, chronic pelvic pain, and

temporomandibular pain. Chronic fatigue syndrome

(CFS) and IBS are overlapping conditions. The two

syndromes share a basic diagnostic approach in that

they rely on symptom reports, in the absence of a

clinically objective marker, to aid in diagnosis or 

to evaluate treatment effectiveness.

IBS is a common problem in the United States and

worldwide; it is thought to exist in about 10 to 17

percent of the U.S. population. Among IBS patients,

there are two to three women for every man. This 

sex-based differential exists in every country with 

the exception of India, which reflects either a sociocultural phenomenon related to healthcare access 

or exposure to different types of amoebae in the 

intestine. The diagnostic criteria for IBS are based 

on the Rome II criteria; the Rome III working group 

is re-examining these criteria, and new criteria may 

be forthcoming in the near future. Unfortunately, 

one survey found that only about 15 percent of 

primary care providers are aware of the existence 

of diagnostic criteria for IBS.

The etiology of IBS remains unclear, but a number 

of promising theories related to its pathophysiology

are under investigation. The theories fall into three

main categories. One is that people with IBS have 

visceral hypersensitivity (i.e., they are sensitive to 

normal stimuli in the bowel, such as gas or fecal

material). A second theory is that IBS is related to

alterations in gastrointestinal (GI) motility or transit. A more recent theory is that IBS is related to a

prior infection or inflammation of the bowel; for

example, people who have had enteritis resulting

from food or water contamination are able to 

date their IBS symptoms to the enteral infection.

IBS can be used as a model of a multisystemic 

disorder because, in addition to lower GI symptoms, IBS features symptoms of the upper GI tract

and bladder, gynecological problems, and somatic

complaints. For example, about 70 percent of people 

with fibromyalgia also have IBS, and about 30 

percent of people with IBS also have fibromyalgia.

Recent studies have examined the overlap between

IBS and gynecological conditions, particularly dysmenorrhea and premenstrual distress syndrome,

which seem to occur more frequently in women 

who have IBS. Like the models for CFS, the model 

for IBS is complex, involving factors such as genetics

and early childhood exposure to stress. The model

includes factors that may trigger symptoms such as

stress and diet and menstrual cycle changes, and

response modifiers and outcomes involving the central, peripheral, and enteric (“little brain”) nervous

systems. Current IBS models address the brain-gut

axis and the dysfunctional communication and 

interaction between the brain and gut.

Among IBS patients, there are two 

to three women for every man.

Issues of sex and gender in IBS fall into four major

categories: stress response, menstrual cycle, affective

symptoms, and sociological issues. Men and women

are different in terms of stress reactivity and responsivity, and the menstrual cycle is an important confounding variable for many women. The overlay of

affective symptoms also is significant, because people

with IBS have higher rates of anxiety and depression.

Sociological gender roles may affect symptom expression, perception, and healthcare-seeking behavior.

Sex and Gender Issues in Multisystemic Illnesses 81

Sex and Gender Issues in Multisystemic Illnesses

Margaret M. Heitkemper, Ph.D.
Because IBS is more prevalent in females, a disproportionate number of women are included in IBS

studies; therefore, more is known about women 

with IBS than about men with IBS. Because the 

menstrual cycle may act as a symptom trigger, it 

is important to consider in which phase of the 

menstrual cycle women should be studied in IBS

research; for example, whether comparison should 

be made at premenses or menses phases when symptoms are likely to be increased or at the follicular

phase when symptoms are low. It is also important 

to consider oral contraceptive use, as well as hormone replacement therapy.

The higher prevalence of IBS in females appears at

puberty; however, IBS is not well characterized in

children. Recurrent abdominal pain, which occurs 

in children, appears to be similar to IBS. Children

with this condition have chronic or recurrent 

abdominal pain that often keeps them from going 

to school, but diagnostic tests fail to reveal pathology. In children, the gender distribution of recurrent abdominal pain is equal, but as children

approach puberty, it emerges predominantly in girls. 

Since IBS is a symptom-based functional disorder,

there is much debate about symptoms assessment.

Some investigators believe that daily diaries are 

more reliable than retrospective recall of symptoms,

such as pain, but retrospective recall may elicit the

individual’s worst experience. In our studies, the 

participants rate their symptoms on a daily basis 

and mark ovulation by use of a home luteinizing 

hormone surge kit, which allows for assessment 

of differences in the menstrual cycle phases. In 

comparisons of women’s daily diaries with men’s

diaries, abdominal pain in women on non-menses 

days looked similar to abdominal pain in men; 

at menses, women had higher levels of pain. 

Women also reported more bloating, both before 

and during menses. Men report greater severity 

of diarrhea whereas women are more likely to 

report constipation.

Most studies on the physiological influence of the

menstrual cycle have compared the mid-follicular

(estrogen with no progesterone) and luteal (estrogen plus progesterone) phases. However, when 

symptoms are influenced by the menstrual cycle, 

they tend to be amplified in the late luteal and 

early menses phases, times of decreasing or low 

estrogen and progesterone. Additional work is 

needed using models of ovarian hormone 

withdrawal; however, the study of women at 

menses can be particularly challenging because 

of the co-occurrence of dysmenorrhea.

Regarding other symptoms, women with IBS report

higher fatigue levels and greater sleep disruption 

than men with IBS. Using daily diaries, we measured

how well women felt in the morning, how rested 

they felt, and how well they believed they had slept.

Those items were then correlated with GI symptoms

on the same day. The data showed a relationship

between poor sleep and GI symptoms: when women

had poor sleep the night before, they reported more

symptoms the next day. The reverse was not true; 

GI symptoms during the day did not result in poor

sleep that night. Although women with IBS subjectively report poor sleep, frequent awakenings, and

feeling unrefreshed in the morning, there are few 

differences when objective sleep indicators are measured using standard polysomnographic measures 

of sleep. However, sleep stage differences do exist

when comparing IBS women with and without 

mood disturbances.

Since IBS is a symptom-based 

functional disorder, there is much

debate about symptoms assessment.

Few studies have examined the roles of estrogen 

and progesterone in GI function. Data from both

humans and rodents indicate that estrogen slows 

gastric emptying rate. GI symptoms, such as heartburn and constipation, are common in pregnancy 

and appear to be related to progesterone or the 

combination of estrogen and progesterone.

Examining GI motility and transit during the 

estrous cycle in female rats in the laboratory is 

challenging. We removed the ovaries from female 

rats and implanted estrogen and progesterone 

pellets in order to examine the hormones’ effects 

on gastric emptying and intestinal transit. Results

confirmed that estrogen slows down intestinal 

transit and gastric emptying. The mechanisms

accounting for these effects remain to be determined; the gut has receptors for estrogen, and 

estrogen may affect nitric oxide synthesis and 

release or act through ion channels. It is possible 

that GI symptoms in women are driven not by 

estrogen and progesterone but by the lack of 

testosterone; however, in a limited number of 

82 Sex and Gender Issues in Multisystemic Illnesses
studies, testosterone has not been shown to have 

a profound effect on bowel motility. Gonadotropinreleasing hormone agonists have been shown in 

small sample studies to be useful in treating conditions such as IBS, although there is concern about

using such drugs over a prolonged period of time.

Currently, there is considerable support for the role 

of visceral hypersensitivity in the pathophysiology 

of IBS. Patients with IBS have increased sensitivity 

to balloon distention in the rectum. Both PET scanning and fMRI techniques have demonstrated that

brain activation patterns differ between IBS and 

controls in response to balloon inflation. Gender 

differences in activation patterns have also been

observed. Studies by Houghton and colleagues have

shown that in non-symptomatic women without 

IBS, no differences in visceral perceptions are seen

across the menstrual cycle; however, in women with

IBS, differences in visceral hypersensitivity are seen

across phases of the menstrual cycle. The time of 

high sensitivity or high pain perception is at menses.

To test whether people with visceral hypersensitivity

are hypersensitive to pain in general, several laboratories have used somatic pain challenges, including

hand ice water immersion. Some have shown no 

differences between IBS and controls, while others

have shown that IBS patients have increased 

somatic pain sensitivity.

Once serotonin has been turned 

on, other chemical mediators—for

example, calcitonin gene-related 

peptide—are likely involved in 

affecting motility of the bowel.

Stress has also been identified as a trigger for IBS

symptoms. Gender differences have been found in 

relation to the stress response, that is, men tend to

respond with greater sympathetic nervous system 

activation. It has been proposed by Taylor that 

women have a “tend and befriend” pattern of 

response to stress. We began to look at the autonomic nervous system in IBS patients using several

approaches. First was to look at catecholamine 

secretion in the urine. Women were asked to void

before they went to bed and to provide first-voided

urine specimens in the morning. In the morning,

women with IBS had higher levels than controls of 

catecholamines and cortisol. Based on that result, 

we began to explore other indices of autonomic 

nervous system functioning including laboratory 

testing, for example, expiration/inspiration ratio,

Valsalva, and postural changes. Overall, no differences were found in these reactivity measures

between individuals with IBS and those without. 

Next, women in the study wore 24-hour Holter 

monitors to record the rhythms of their heart rates 

in a naturalistic environment. Differences emerged

between IBS and non-IBS individuals, especially during the nighttime hours when the women had low 

levels of heart rate variability (vagal tone). Individuals typically have the highest levels of vagal tone 

during sleep, but those with IBS exhibited a dampened response. Among IBS subjects categorized by

pain experiences (time of pain and severity of pain),

women whose pain was rated as severe and unrelated

to eating had the lowest level of vagal tone. Because 

it is known that psychological states can influence

autonomic nervous system balance indicators, the 

subjects were also compared for history of depression

and anxiety. Individuals who had a history of panic

disorder, agoraphobia, depression, or dysthymia 

exhibited low levels of heart rate variability (lower

vagal tone) compared to individuals with no history 

of mood disorders. When examining a multisystemic

functional disorder, such as IBS, researchers should 

be aware of the coexistence of other conditions, 

such as depression, and their impact on physiological responses.

IBS, CFS, and related disorders are disruptive to 

individuals, and numerous studies have demonstrated reduced quality of life in those who have

these conditions. Women with IBS report bloating,

clothes not fitting, being unable to zip their pants,

having the sensation of weight gain and fullness, 

and urgency. The psychosocial implications of these

symptoms on body image perception remain largely

unexplored. The disturbance in body image may

explain the greater healthcare-seeking behavior 

noted in women than in men.

Future directions for research encompass several

areas. Is there a common pathophysiology that 

underlies conditions such as CFS and IBS? Is that

pathophysiology related to serotonin or another 

neurotransmitter, to an immune alteration, to 

autonomic nervous system dysregulation, or 

to hypothalamic-pituitary-adrenal (HPA) dysregulation? Does reproductive status or cycling 

make a difference?

Sex and Gender Issues in Multisystemic Illnesses 83
While serotonin is important in the brain, most 

serotonin in the body is housed in the GI tract, 

including enteric neurons. Serotonin also is found 

in enterochromaffin cells, which are closely linked

with the mucosal surface and nerve endings. In the

gut, serotonin can play a role in pain transduction 

and transmission. There are a variety of serotonergic

receptor subtypes and mediators in the bowel, as in

the brain. Once serotonin has been turned on, other

chemical mediators—for example, calcitonin generelated peptide—are likely involved in affecting 

motility of the bowel.

Studies of serotonergic agents to manage IBS 

show that these drugs, at the doses studied, work 

in women but are less effective in men. The U.S. 

Food and Drug Administration has approved the

serotonergic drugs for women, which underscores 

the possibility of basic differences between men 

and women, either in serotonin release, receptors, 

or metabolism. Related IBS research is investigating polymorphisms in the 5-HT3 receptor and the 

SERT promoter. Other models of IBS, including 

the post-infectious model, represent additional

avenues for further research. This link involves 

further exploration of the role of inflammation 

in the initiation or persistence of IBS symptoms.

Recent clinical advances have occurred in understanding IBS treatment with probiotics. Studying 

the systemic effects of changing the bowel flora,

including activation of cytokines in the GI tract, 

may reveal effects reaching beyond the bowel.

A number of important areas should be explored,

including the role of early environmental exposure 

in the evolution of disorders, such as IBS and CFS,

and the possibility of genetic predisposition to 

those disorders. Autonomic nervous system and 

HPA alterations may be important predictors in 

individuals with severe symptoms.

Cognitive behavioral therapies are effective for 

treating disorders such as IBS and CFS; however, 

while these therapies can reduce symptoms, they 

do not change the basic underlying pathophysiology. We recently completed a study of cognitive 

behavioral therapy for women with IBS. The 

therapy reduced symptoms, reduced healthcare 

utilization, and increased quality of life, but it 

did not affect autonomic nervous system balance 

or catecholamine levels.

Discussion

Dr. Goldstein: Regarding catecholamine systems,

adrenaline or epinephrine is a potent inhibitor 

of gut motility. The first bioassay preparation 

by Walter Cannon almost a century ago, about 

the effects of emotion on adrenaline release, 

depended on adrenalin relaxing the gut. In concept diagrams linking the adrenal system with 

the gastrointestinal tract, it is important to 

include that inhibitory effect of adrenaline. 

In addition, most of the dopamine made in 

the body is not made in the brain or the autonomic nervous system but in the gut. This 

dopamine appears to be part of a third type 

of catecholamine system. It is neither a neurotransmitter nor a hormone, but rather an

autocrine/paracrine substance—something 

that is made in, released by, and acts on cells 

locally. In dealing with catecholamine systems, 

it might be worthwhile to explore the effect on 

IBS of drugs that act on dopamine receptors.

Dr. Heitkemper: I agree with your point. 

These agents have not been explored.

Dr. Van Konynenberg: In the past few years, 

Mark Pimentel at the University of California,

Los Angeles, has published papers that support 

the hypothesis that IBS is caused by bacterial 

overgrowth of the small intestine, resulting from 

the lack of the cleansing peristaltic waves that a 

normal person has about 2 hours after eating. 

Does your work relate to why those waves 

might not be stimulated in people with IBS?

Dr. Heitkemper: We have not studied colonic 

motility in patients with IBS. The results related 

to normalization of motility following antibiotic 

treatment are interesting, but it is unknown 

whether these results can be sustained over 

time. The other question this brings up is whether 

gender differences or menstrual cycle differences 

may account for either the gender differences in

migrating motor complexes or the amplification 

of symptoms in women around menses.

Dr. Baraniuk: Dean Befus at the University 

of Alberta has conducted some interesting 

studies on sympathetic innervation causing 

the release of gut hormones that have CNS 

and immune effects.

84 Sex and Gender Issues in Multisystemic Illnesses
Sex and Gender Issues in Multisystemic Illnesses 85

Dr. Heitkemper: The weakness of our methodology 

is that we do heart rate variability while looking 

at a gut-related condition. Ideally, we would monitor parasympathetic innervation of the upper and

lower GI tract, but at this time that is not possible

with our methodology. We have not explored the

release of gut hormones in IBS. The vagus does

innervate the upper part of the gut, but there 

are different branches, and the question is whether

they react the same way. We have contemplated

measuring pancreatic polypeptide, which is linked 

to autonomic nervous system function.

Most of the dopamine made in the body is not made in the brain 

or the autonomic nervous system but in the gut. This dopamine 

appears to be part of a third type of catecholamine system. It is 

neither a neurotransmitter nor a hormone, but rather an autocrine/

paracrine substance—something that is made in, released by, and 

acts on cells locally.

At the time we conducted a family study to test

the hypothesis that fibromyalgia aggregates 

in families, three prior studies had reported

preliminary evidence for aggregation of fibromyalgia in families, but the studies were limited by small 

sample sizes and lack of a comparison group. Our

study used a case-control design in which the case

families had a member (proband) with fibromyalgia

and the control families had a member who did not

have fibromyalgia but had rheumatoid arthritis.

Patients with rheumatoid arthritis were chosen 

as the comparison group for several reasons:

• Rheumatoid arthritis is also a chronic pain 

condition that predominantly affects women.

• We wanted to draw subjects from the same 

study base, and both proband groups were

recruited from the same rheumatology 

outpatient clinic.

• We wanted to reduce the possibility of 

ascertainment bias due to the treatmentseeking effect for a chronic pain condition.

A second hypothesis was that fibromyalgia in a

proband is associated with increased tender points

and higher levels of pain in relatives. Fibromyalgia 

is defined not only as chronic widespread pain, but

also as the presence of tender points. We decided 

to investigate whether tender points themselves also

aggregate in families, measuring tender points 

using a dolorimeter, which provides a measure 

of pressure-pain thresholds.

The third hypothesis was that fibromyalgia coaggregates with major mood disorder (major 

depressive disorder or bipolar disorder) in families.

Hudson and colleagues discovered that fibromyalgia

was associated with a high familial rate of mood 

disorders. However, the high prevalence of mood 

disorders in families of patients with fibromyalgia

could have been due to the familial aggregation 

of mood disorders. We addressed the methodological

limitations of the prior family studies and controlled

for the effects of major mood disorders in probands 

to confirm the co-aggregation of fibromyalgia with

major mood disorder in families.

We were also interested in gathering preliminary 

data on the co-aggregation of fibromyalgia with 

other disorders that are thought to be related to

fibromyalgia, including chronic fatigue syndrome,

irritable bowel syndrome (IBS), migraine, 

and anxiety disorders. 

In the design of the family study, the age range 

of the probands was restricted to 40 to 55 years of

age so that first-degree relatives would be approximately the same age within the type of relative 

(child, sibling, and parent), and between proband

groups, and because both age and cohort effects 

exist in the prevalence of major mood disorder and

possibly also in fibromyalgia. At least one relative

was required to be available for evaluation.

Diagnostic procedures included the Structural 

Clinical Interview for DSM-IV (SCID) for assessing lifetime psychiatric illness, with supplemental

modules for fibromyalgia, CFS, IBS, and migraine. 

A revised version of the Family Interview for 

Genetics Study (FIGS) was used with relatives to 

elicit information about the non-interviewed firstdegree relatives. The tender point exam used a 

Fischer dolorimeter. The myalgic score was the 

sum of the dolorimetry pressure-pain threshold 

results for all 18 tender point sites, and the tender

point count was determined by the number of 

tender points with a threshold of <4 kg/cm2

. 

Pain was assessed with visual analog scales that 

determined pain right now, worst pain during 

the past 6 months, and average intensity of pain 

during the last 6 months.

Family Studies in Fibromyalgia 87

Family Studies in Fibromyalgia

Lesley M. Arnold, M.D.
To evaluate the familial aggregation of fibromyalgia,

we used a univariate predictive logistic regression

model, with the presence or absence of fibromyalgia

in a relative as the outcome, and the presence or

absence of fibromyalgia in the proband associated

with that relative as the predictor. To test the coaggregation of major mood disorder with fibromyalgia, we used a multivariate logistic regression model,

with bivariate disorder status of a relative (the presence or absence of fibromyalgia and major mood 

disorder) as the outcome and bivariate disorder 

status of the corresponding proband as the predictor. The model estimates an aggregation odds ratios

for the familial co-aggregation of fibromyalgia with

major mood disorder, while controlling for the 

effects of the familial aggregation of fibromyalgia, 

the familial aggregation of major mood disorder, 

and the co-occurrence within persons of fibromyalgia with major mood disorder.

We gathered information on more than 500 relatives of the probands with fibromyalgia and on 

more than 200 relatives of the probands without

fibromyalgia, and interviewed and examined a 

subset of those individuals.

The presence of lifetime comorbid diagnoses for 

the fibromyalgia and rheumatoid arthritis probands

was typical for these patients in tertiary care settings.

Major mood disorder, anxiety disorders, CFS, IBS, and

migraine were more common in the probands with

fibromyalgia than in those with rheumatoid arthritis. 

Fibromyalgia was found to aggregate strongly in 

families. The estimated odds of fibromyalgia in a 

relative of a proband with fibromyalgia were 8.5

times the odds of fibromyalgia in a relative of a

proband with rheumatoid arthritis (P = 0.0002). 

Only three cases of fibromyalgia were seen in the

male relatives overall; therefore, aggregation was 

driven primarily by the effect of the female relatives.

The relatives of probands with fibromyalgia displayed significantly higher levels of tenderness—

both increased tender points and decreased myalgic

score—than was displayed in the relatives of probands with rheumatoid arthritis. There was also 

a trend toward higher levels of pain in relatives 

of fibromyalgia probands, and male relatives were

significantly less tender than were female relatives.

However, there was no significant group-by-sex 

interaction; males in the fibromyalgia proband 

group were more tender than males in the control

proband group and the same was true for females.

Fibromyalgia co-aggregated significantly with 

major mood disorder (odds ratio = 1.8; P = 0.013). 

No significant co-aggregation was found for the 

other disorders of interest, possibly because the 

study was underpowered for that purpose, but 

some trends were observed: anxiety disorders and 

eating disorders were more common in the relatives 

of probands with fibromyalgia than in relatives 

of rheumatoid arthritis probands, but there was 

no difference in the prevalence of substance use 

disorders between the relative groups.

The finding that fibromyalgia aggregates in families

has important clinical and theoretical implications.

Familial aggregation of fibromyalgia supports the

validity of fibromyalgia, which is currently diagnosed

with criteria that were developed by expert consensus

and limited by the lack of definitive laboratory or

88 Family Studies in Fibromyalgia
Family Studies in Fibromyalgia 89

pathological findings. In addition, familial aggregation of fibromyalgia suggests a possible genetic 

contribution to the etiology of fibromyalgia. 

The study also revealed that fibromyalgia in probands was associated with increased tender points

and decreased myalgic scores in relatives and that 

this association was independent of the presence of

fibromyalgia or major mood disorder in the families.

These findings support the validity of pressure-pain

thresholds in fibromyalgia and suggest that there 

may be inherited factors in pain sensitivity. The coaggregation findings suggest that fibromyalgia shares

some familial factor or set of factors with mood 

disorders, but also has a factor or factors that are

independent of mood disorders. The data are not 

consistent with the hypothesis that fibromyalgia is

simply caused by mood disorder; rather, they are 

consistent with the hypothesis that fibromyalgia 

and mood disorders share important common 

and possibly heritable causal factors.

The study’s limitations included low power to 

detect co-aggregation with other disorders of 

interest; additional research with more subjects 

is needed. Familial aggregation or co-aggregation 

does not prove underlying genetic factors, although 

it is suggestive. Our next steps are to continue to

recruit families to allow for greater power to test 

the co-aggregation of other disorders and to reexamine the issue of pain in relatives by using 

more sensitive measures or by recruiting more 

families. Fibromyalgia may be caused in part by

genetic factors, which may be shared with other 

disorders, particularly mood disorders.

Further Reading

Arnold LM, Hudson JI, Hess EV, Ware AE, Fritz DA,

Auchenbach MB, Starck LO, Keck PE Jr. Family study

of fibromyalgia. Arthritis Rheum 2004;50:944-952.

Buskila D, Neumann L, Hazanov I, Carmi R. Familial

aggregation in the fibromyalgia syndrome. Semin

Arthritis Rheum 1996;26:605-611. 

Buskila D, Neumann L. Fibromyalgia syndrome (FM)

and nonarticular tenderness in relatives of patients

with FM. J Rheumatol 1997;24:941-944.

First MB, Spitzer RL, Gibbon M, Williams JBW.

Structured clinical interview for the DSM-IV Axis I

disorders-patient edition (SCID-I/P), Version 2.0 New

York: Biometrics Research Department, New York

State Psychiatric Institute, 1995.

Fischer AA. Pressure algometry over normal muscles.

Standard values, validity, and reproducibility of pressure threshold. Pain 1987;30:115-126.

Hudson JI, Hudson MS, Pliner LF, Goldenberg DL,

Pope HG Jr. Fibromyalgia and major affective disorder: a controlled phenomenology and family history

study. Am J Psychiatry 1985;142:441-446.

Hudson JI, Goldenberg DL, Pope HG Jr, Keck PE Jr,

Schlesinger L. Comorbidity of fibromyalgia with medical and psychiatric disorders. Am J Medicine 1992;

92:363-367.

Hudson JI, Laird NM, Betensky RA. Multivariate

logistic regression for familial aggregation of two 

disorders: I. Development of models and methods. 

Am J Epidemiol 2001;153:501-505.

Hudson JI, Laird NM, Betensky RA, Keck PE Jr, 

Pope HG Jr. Multivariate logistic regression for 

familial aggregation of two disorders: II. Analysis 

of studies of eating and mood disorders. Am J

Epidemiol 2001;153:506-514.

Laird NM, Fitzmaurice GM, Schwartz AG. The 

analysis of case-control data: epidemiologic studies 

of familial aggregation. In: Sen PK, Rao CR, editors.

Handbook of Statistics, Vol. 18. New York: Elsevier

Science; 2000. p. 465-482.

Maxwell ME and the NIMH Diagnostic Center for

Psychiatric Linkage Studies: Family interview for

genetic studies (FIGS). Washington, DC: National

Institute of Mental Health, 1992.

Pellegrino MJ, Waylonis GW, Sommer A. Familial

occurrence of primary fibromyalgia. Arch Phys Med

Rehabil 1989;70:61-63.

The finding that fibromyalgia aggregates in families 

has important clinical and theoretical implications.

Dr. Arnold also presented results of a genetic study of fibromyalgia under review for publication that could not be included in this report.

An ideal study design system is needed that standardizes the assessment of a particular illness.

Using instruments in a similar fashion should

enable comparison of studies across study sites. If

samples are collected, processed, and examined in 

the same way, it should be possible to interpret the

data and reach a greater understanding of the illness. 

Biomarker discovery involves finding something in 

a sample or an individual that defines or identifies a

disease. Good biomarkers and knowledge of where

and in what part of the lifespan the biomarker is

found have the potential to increase understanding

about disease pathogenesis. There are a number of

places in a disease process to discover biomarkers

that would help provide an understanding about 

susceptibility, the dose of the biomarker, the mode 

of action of that biomarker, and the disease pathogenesis and etiology. 

It is unlikely that illnesses such as chronic fatigue 

syndrome, irritable bowel syndrome (IBS), and 

many neuroendocrine disorders will have a single 

biomarker, molecule, or gene to explain the whole 

illness. Many factors will likely be involved in any 

illness process including genes, gene expression, 

environment, and behavior.

CFS is a complex illness. The Centers for Disease

Control and Prevention’s (CDC) approach to studying CFS is highlighted and briefly reviewed in the

Chronic Fatigue and Immune Dysfunction Syndrome

Association of America’s newsletter in an article entitled “CDC Shifts to High-Tech Clinical Studies.”

CDC’s CFS program is an integrated multidisciplinary

program that seeks to identify the number of people

who suffer from CFS and then to enroll these people in

studies that seek to define the illness. We now know

that the number of people with CFS in the United

States ranges from 500,000 to 1 million adults.

In order to accurately determine the incidence of

CFS, it is necessary to define the illness. A case definition was developed in 1988 and further refined in

1994; a process is underway to refine the definition

even further by using standardized instruments and

similar study designs so that any case definition can

be based on empirical information rather than on

consensus. Once people with CFS are identified, 

samples are collected from them in an attempt to

decipher the pathophysiology of the disease, seeking

to identify causal agents or risk factors as well as

biomarkers or diagnostic markers. It is important 

to identify a good biomarker for CFS so that the 

illness is identifiable and is recognized as a legitimate illness by healthcare providers.

It is unlikely that illnesses such as CFS,

IBS, and many neuroendocrine disorders

will have a single biomarker, molecule,

or gene to explain the whole illness.

The CDC also attempts to educate people about CFS.

When more people believe that CFS exists, a more concerted scientific, research, and medical effort to understand and treat the disorder will become possible.

The CDC’s CFS research program uses populationbased studies, model studies, and clinical studies.

These studies include a population-based study 

that has been underway in Wichita during the past 

5 years, an exercise model study, a post-infected

fatigue model study, interferon alpha challenge 

studies, treatment studies, hepatitis C studies, and 

a study of interleukin-6. Each of these studies integrates microbiology, immunology, endocrinology, 

neurology, epidemiology, genomics, and proteomics 

to develop an understanding of the illness.

Biomarker Discovery in Illnesses with No Lesions 91

Biomarker Discovery in Illnesses with No Lesions

Suzanne D. Vernon, Ph.D.
The CDC is currently conducting gene expression

profiling studies for biomarker discovery and to 

further our understanding of disease pathogenesis. 

The Wichita population-based study is a randomdigit-dialing telephone survey of about 40,000 

households. According to the U.S. Census Bureau,

Wichita’s demographics represent the U.S. population in general: the distribution of various races, 

ethnicities, and sex is represented in Wichita. This

study began in 1997 and was designed to estimate 

the prevalence of CFS and other fatiguing illnesses 

in the population. Individuals identified by phone 

as having fatigue were followed up with a more

detailed interview. If it was determined that the 

individuals had a chronic fatigue-like illness, they 

were invited to come in for clinical participation 

and were followed over time. Over the course of 

the study, 90 people with CFS were identified. 

A random sample of non-fatigued individuals 

was also brought into the clinic—incident cases 

or cases that were misdiagnosed originally at baseline. The study results are generalizable to the 

U.S. population.

A post-infected fatigue study involves Lloyd’s 

cohorts from the University of New South Wales 

in Australia. It is a longitudinal study of acute 

infection with Epstein-Barr virus, Ross River 

virus, or Coxiella (a rickettsial agent that causes 

Q fever). All three infections are known to result 

in a chronic fatiguing illness. Ross River virus, like

influenza, is an RNA virus. Specific to Australia, 

Ross River virus is a typical arbovirus that is 

carried by mosquitos, resulting in a fatiguing 

illness with arthralgia and myalgia. These three 

agents infect different types of people: the EpsteinBarr cohort is composed predominantly of young 

men and women, the Ross River virus affects a 

mix of people throughout the Australian continent,

and Q fever predominantly affects men working 

in the animal processing industry. The subjects 

were enrolled based on acute infection and an

immunoglobulin M response, and then are followed over time. Currently, many of the subjects 

have been followed for up to 3 years post-infection.

If a gene is actively being expressed 

in the PBMC sample, it will hybridize 

to the corresponding gene spot on 

the microarray.

Another CDC study conducted with Jones at

National Jewish Hospital is an exercise challenge

study that involves challenging patients with a 

stationary bicycle and examining blood samples

before and after the challenge.

One of the biggest hurdles to studying CFS is that

there is no known lesion; nothing anatomically 

accessible can be biopsied. We had to make a 

decision on what type of sample would be representative of CFS or would be potentially useful 

for biomarker discovery. We chose to study peripheral blood as a representative sample of CFS. The

rationale for that choice was that, because blood 

circulates through the body continually, cells and

serum could serve as sentinels of various disease

processes. Cells carry signals throughout the body

and various organs, and serum bathes all the organs

of the body and contains anything that the organs 

do not want, which could be an indicator of 

various disease processes.

All of our genomics studies use the peripheral 

blood mononuclear cells (PBMCs). The genomics

approach we use to profile gene expression is called

microarray technology. Microarrays are glass microscope slides spotted with thousands of cDNAs or

oligonucleotides. A probe made from the subject’s

PBMC sample is put on the microarray and allowed

to hybridize. If a gene is actively being expressed 

in the PBMC sample, it will hybridize to the 

corresponding gene spot on the microarray.

This hybridization reaction is detected with a 

sensitive gold and white light system; spots that

appear bright are clearly positive and those that 

cannot be seen are obviously negative. This technique is a rich and relatively low-tech approach 

that derives much information from one sample.

The reason we are relatively comfortable and 

confident with using PBMC samples for gene 

expression profiling and biomarker discovery 

is that a number of studies have shown that 

PBMCs in both normal and disease states traffic 

back and forth through the blood-brain barrier,

either through primary signaling or secondary 

messenger systems. The great dynamic between 

what happens in the body and what happens 

in the head may allow researchers to decode 

disease processes.

92 Biomarker Discovery in Illnesses with No Lesions
By using gene expression profiling of the peripheral

blood, we have been able to differentiate individuals

with and without CFS. Recently, we have also been

able to demonstrate with gene expression profiling

that CFS is a heterogeneous illness. Dr. Toni Whistler

in our group examined samples from 25 CFS subjects

in the Wichita study—all were women in their 40s—

and attempted to use gene expression profiling to

determine whether the CFS subjects could be distinguished. Our hypothesis was that since symptoms

define CFS, these symptoms should correlate with

specific gene expression patterns; the result was that

they did not. One group of subjects had sudden onset

and another group had gradual onset of illness, and

researchers identified only 112 out of 4,000 genes

that were different between the two groups. Fifty percent of the genes that were upregulated in the rapid

onset individuals were metabolism genes, although 

a number of different functional families were seen,

including immune system genes and cell adhesion.

Can the brain be profiled by looking at the blood? 

An approach taken by the CDC to answer that question involves an informatic query of blood cDNA

databases. Researchers identified 1,800 genes involved

in psychoneuroendocrine immune pathways, in an

attempt to determine what occurs with the HPA axis

and the brain by looking at the blood. They created a

normal blood cDNA database that contained 45,000

genes and queried it for 1,800 genes, finding that

about 1,400 genes are expressed in the blood. Of

these genes, 24 percent are endocrine, 14 percent 

are neurotransmitters, 40 percent are immune, and 

22 percent are involved in various aspects of other

functions. About 5 percent of the genes are neurotransmitter genes expressed in their PBMCs. The

CDC is optimistic that peripheral blood will provide 

some indication of what occurs in the brain.

Peripheral blood expression of hormone receptors

was found—the hormone responsive protein ZNF147 and several GABA-nergic system proteins.

To attempt to predict who will not recover from 

acute infection with Epstein-Barr virus, and because 

of a metabolic abnormality in some CFS subjects, 

the CDC gene expression databases were queried for

metabolic genes. Three years of data are available on

those individuals, so it was possible to discern who

recovered and who stayed sick. The subset of genes

that separates the sick individuals from the recovered

individuals falls into metabolic pathways—mitochondrial transport and lipid metabolism genes.

The CDC’s work can be credited to a comprehensive

multidisciplinary approach that includes researchers

within and outside the CDC, including collaborators

from Emory University, National Jewish Hospital,

Australia, Karolinska Institutes, University of Miami,

Chronic Fatigue and Immune Dysfunction Syndrome

Association, APS Associates, University of Texas MD

Anderson Cancer Center, and an international group

that has been working with the CDC on the CFS 

case definition.

Discussion

Dr. Natelson: As a believer in the brain being one 

of the organs involved in CFS, I have recently

obtained preliminary findings from spinal fluid. 

The brain probably is involved in CFS, which 

should be considered when choosing a body fluid 

to study. It also is important to focus on fMRI.

Dr. Vernon: I agree, but it is difficult to obtain spinal

fluid. While it can be done in small numbers at relatively few sites, it is difficult to do on a population

scale. Blood, however, can be obtained and processed

relatively easily. It will be incumbent upon us to be

able to decode the information we find and relate it 

to what occurs in the brain. We hope that through animal studies we will be able to look at gene expression

in the brain and blood of rats and see if they correlate

and, if not, determine how to decode that information.

Dr. Buchwald: You studied most of the people who

reported an acute onset a long time after that onset,

and apparently the metabolic genes were turned on.

The individuals may have been sick for 6, 8, or 

10 years, and it is questionable whether the acute

onset is reliable.

Dr. Vernon: My rationale was to ask whether or not

we can predict who is most susceptible to developing

a chronic fatiguing illness when they get Epstein-Barr

virus or some kind of chronic or acute stressor. It was

proposed as a quick, hypothesis-generating query. I

looked at a number of our favorite hypotheses. For

example, in people I knew who were acutely ill and

did not get better, I could not find any differences 

in clustering when I looked at some of the cytokine

receptors, despite some evidence of downregulation of

the receptors. When I queried some of the metabolic

pathways, I started to see differences. Perhaps subtle

differences predispose us to certain types of stressors

or infections and make it difficult to recover.

Biomarker Discovery in Illnesses with No Lesions 93

Therapeutics 95

Session Five: Therapeutics

Chair: Dimitris A. Papanicolaou, M.D.

Regardless of its clinical significance and regardless of the symptoms and disability it causes, chronic

fatigue syndrome (CFS) has no cure at this point. CFS is multifactorial and likely represents more 

than one disorder. The literature reveals studies that have used pharmacological treatments and a 

few studies that have used nonpharmacological treatments; all were met with variable success. It is not yet 

possible to state that one treatment works and another one fails, but it is possible that some treatments will

work with some groups of people.

I

ndividuals who went to the first Gulf War and

returned with otherwise unexplained pain, fatigue,

and other symptoms have something similar or

identical to chronic fatigue syndrome (CFS), fibromyalgia, or multiple chemical sensitivity somatoform

disorders. Studies that have been conducted on Gulf

War illnesses, fibromyalgia, and CFS during the last 

3 years have provided insight into what does and

does not work in treating these diseases.

The Veterans Administration Cooperative Trials

Network is a significant resource for conducting 

clinical trials. Researchers design a trial and then 

the Cooperative Trials Network conducts the trial;

researchers only need to design the trial and analyze

the data at the end.

Nonpharmacologic Therapy

Cognitive behavioral therapy and exercise have been

shown to work well in single-site efficacy trials. In

moving from an efficacy design to an effectiveness

design, a major issue is whether these therapies work

well in routine clinical practice for individual patients. 

Many drugs have been shown to be effective in 

short-term, single-site trials conducted at academic

medical centers. However, studies conducted at academic medical centers in many cases do not follow

good clinical practice and do not have in place the

kind of stringent monitoring requirements and other

compliance issues that characterize trials that hope 

to garner FDA approval. Phase II and Phase III trials

conducted in the context of an investigational new

drug are generally conducted in a more stringent

manner than other types of studies.

A large study conducted within the Veterans

Administration (VA) and the Department of Defense

(DoD) healthcare system, published recently in

JAMA, involved about 1,100 veterans of the first 

Gulf War who were being seen in 18 VA and two

DoD health care centers. About 700,000 U.S. troops

were deployed to the first Gulf War, with few combat-related casualties. Within 6 to 12 months, people

who served in the war began to return and to complain of difficulty with memory, pain, fatigue, and

several other symptoms. The symptoms that Gulf 

War veterans suffer represent the same clusters of

symptoms that occur in the general population and

are called fibromyalgia and CFS. The term coined 

by the Centers for Disease Control and Prevention

(CDC) to describe this constellation of symptoms 

and syndromes—as it occurred in Gulf War veterans

and as it occurs in the general population—is chronic

multisymptom illnesses (CMI).

Although CMI came to the forefront after the first

Gulf War, military historians in the United States and

the United Kingdom have noted that after every war

since the mid-1800s—as far back as reliable records

exist—there have been soldiers who returned with

otherwise unexplained pain, fatigue, and memory

problems. After every war, this constellation of health

problems has been called something different: Da

Costa’s Syndrome, soldier’s heart, effort syndrome,

and shell shock. The primary symptoms are the 

same, no matter what these problems are called.

The symptoms that Gulf War veterans

suffer represent the same clusters of

symptoms that occur in the general

population and are called fibromyalgia

and CFS.

The U.S. Government has spent about $240 million

looking at the effect of specific exposures in the theater of operations in the first Gulf War. One study

implied that individuals who received vaccines at 

the time of deployment were more likely to develop

symptoms than if that same set of vaccines had been

Innovative Treatments in CFS 97

Innovative Treatments in CFS

Daniel Clauw, M.D.
given 6 months prior to deployment. With the exception of that single study, no other study has linked

any specific exposure in the first Gulf War to any of

the symptoms of these post-deployment syndromes.

In 1999, the CDC defined CMI as comprising several

factors: multifocal pain; fatigue severe enough to limit

activities; and difficulties with cognition, memory, or

mood. Sometimes cognitive and memory problems 

are separate from mood and sometimes they are

linked together. Under this definition, 10 to 15 percent of the population of the United States meet 

the criteria for CMI. The aggregate prevalence of

fibromyalgia (which affects approximately 4 percent

of the population), CFS (affecting less than 1 percent

of the population), and somatoform disorders (affecting 4 to 5 percent of the population) add up to about 

10 percent of the population.

We hypothesized, based on previous data in fibromyalgia, CFS, and other chronic medical illnesses,

that exercise and cognitive behavioral therapy (CBT)

would lead to improvements in physical function in

individuals with CMI. Furthermore, we hypothesized

that adding CBT and exercise together would produce either additive or synergistic effects—people

would show more improvement when the two 

therapies were combined than if they received 

either therapy separately.

Under this definition, 10 to 15 percent

of the population of the United States

meet the criteria for CMI.

The definition of CMI that we used to create inclusion criteria was that research participants had to be

Gulf War veterans with two or more of the following symptoms: fatigue limiting usual activity, pain in

greater than two body regions, and neurocognitive

symptoms. These symptoms had to have begun after

August 1990 (when the first Gulf War began), had 

to have lasted for more than 6 months, and had to 

be present at the time of screening. About 1,100 

veterans satisfied these eligibility criteria and were

randomized to one of four treatment arms: usual 

care alone, usual care plus CBT, usual care plus 

exercise, or usual care plus CBT and exercise.

Both CBT and exercise were administered in groups

of three to eight. The sessions for both CBT and 

exercise were 60 minutes long, with the combined

CBT and exercise group lasting 90 minutes. These

treatments were administered for 3 months, but 

the primary outcome measure was the proportion 

of individuals who had a clinically meaningful improvement in their physical component summary

score of the SF-36 at 1 year. Instead of the outcomes

being measured at 3 months at the end of the trial,

the primary outcome measure was examined at 1

year, looking for a sustained improvement in function after people had received these therapies.

Secondary outcome measures included pain, fatigue,

cognitive symptoms, distress, and mental health functioning based on the SF-36. Because these were veterans, 85 percent of the subjects were men; their mean

age was 40 years. Although they only needed two 

of three symptoms to meet criteria for CMI, 81 percent of the individuals had all three symptoms: pain,

fatigue, and memory problems. The mean duration 

of symptoms was about 7 years, which was expected

because the trial was started about 7 years after the

end of the war.

Using Prime MD, a screening instrument for psychiatric comorbidities, we found that about 45 percent

of the subjects had present major depressive episodes

or dysthymia, 35 percent had an anxiety disorder, 

and 43 percent had post-traumatic stress disorder. 

In total, 65 percent of the individuals in this trial 

had one of these three disorders, and 65 percent 

of subjects either had pending disability status or

were receiving disability payments.

Primary data analysis showed a modest improvement in physical function in the group that received

CBT, but not in the group that got exercise alone. 

In the exercise-alone group, no difference was observed compared to usual care. In the two groups 

that received CBT, about 7 percent more of those

individuals showed clinically meaningful improvement

in physical function at 1 year. Exercise produced

much more improvement in individual symptoms,

whereas CBT led to less improvement in individual

symptoms such as pain, mental health, and cognitive

function. Exercise led to improvement in symptoms

and CBT led to improvements in function but, 

surprisingly and disappointingly, no additive or 

synergistic effects between CBT and exercise were

observed. Subjects who received both treatments were

not any more likely to improve than were subjects

who received one or the other treatment.

The effect sizes observed in this trial were significantly less than the effect sizes seen in previous 

98 Innovative Treatments in CFS
single-site efficacy trials of either exercise or CBT, 

in either fibromyalgia or CFS. Several interpretations are possible. The hypothesis could be wrong:

perhaps Gulf War illness is not the same as fibromyalgia or CFS; however, many data suggest that 

it is at least very similar and probably identical to

fibromyalgia and CFS. This patient population was

unusual in that it contained a high proportion of

people who were either presently on disability or

had a pending disability status. When predictors 

of outcomes in this study were examined, it was

clear that people who were either on disability or

had pending disability claims were much less likely

to respond to therapy. Given that 65 percent of 

subjects in this trial were in that situation, this 

variable had a powerful effect on study results, 

and the effect of being disabled likely overwhelmed any treatment effect in the study.

A number of compounds have been

studied in fibromyalgia and CFS that, in

one way or another, affect monoamines.

Some drugs raise serotonin, some raise

norepinephrine, some raise dopamine,

and some raise a combination.

Another predictor of outcome was tender points,

defined as a sedimentation rate for distress; in population-based studies, they are highly correlated with

individual distress levels. Subjects who had greater

numbers of tender points were less likely to experience improvement in their physical function, pain, 

or fatigue. It is likely that the relationship between

tender points and unresponsiveness to therapy is a

surrogate for distress being unresponsive to therapy.

Personality disorder was a statistically significant 

predictor of poor outcome with respect to physical

function, although not in other domains. Presence of

a personality disorder was a much stronger predictor

of poor outcome than was the presence of a mood

disorder. Presence of a psychiatric disorder or the

number of psychological disorders was not predictive of unresponsiveness to therapy.

Conclusions of this study are: 1) CBT had a 

marginally significant impact on self-reported physical

function in veterans with Gulf War illness; 2) exercise

resulted in improvement in symptoms and; 3) there

were no synergistic or additive effects. The magnitude

of these changes was modest. This study also points

out the differences between efficacy studies and 

effectiveness studies.

Pharmacologic Therapies

Use of staphylococcus toxoid in individuals who meet

criteria for both CFS and fibromyalgia is innovative

and unique. No one knows why this treatment may

be working. An abstract and manuscript published in

the European Journal of Pain in 2002 discusses this

treatment. Individuals who met criteria for fibromyalgia and CFS were randomized to receive weekly injections for 6 months of either staphylococcus toxoid or

placebo. The primary outcome was the proportion of

individuals who noted a 50 percent improvement on 

a subscale of the Comprehensive Psychopathological

Rating Scale. (This subscale was not commonly used,

which is somewhat problematic.) In an intent-totreat analysis, the researchers showed a 65 percent

response rate in the active treatment group versus 

an 18 percent response rate in the placebo group.

Since that time, the maker of staphylococcus toxoid

has decided that it cannot guarantee uniform purity,

so investigators are not likely to go further even

though initial results appeared somewhat promising.

Pregabalin is a compound under development by

Pfizer. Its method of action is not clear, but Pregabalin

is structurally similar to Neurontin, a GABA (gamma-aminobutyric acid) penton. One study compared

Pregabalin at 450 milligrams/day, 300 milligrams/day,

and 150 milligrams/day to placebo. A large number 

of subjects were randomized to each arm of the trial; 

1 week of titration was followed by 8 weeks of therapy. About 20 to 25 percent of the subjects withdrew.

About 29 percent of the subjects (a statistically 

significant number) experienced a 50 percent improvement in pain in the 450-milligram dose, as compared

to 13 percent of those in the placebo dose. The 450-

milligram dose also led to statistically significant

improvements in patient global improvement—

whether subjects report they are better, unchanged, 

or worse than when they began the trial.

A number of compounds have been studied in

fibromyalgia and CFS that, in one way or another,

affect monoamines. Some drugs raise serotonin, 

some raise norepinephrine, some raise dopamine, 

and some raise a combination. Selective serotonin

reuptake inhibitors raise serotonin. Another class 

of compounds that raise both serotonin and norepinephrine is the tricyclic compounds, some of which

have almost equal effects on serotonin and norepinephrine, and some tricyclics are almost entirely 

Innovative Treatments in CFS 99
noradrenergic compounds. (Pharmacologically they

are quite different, although they are often grouped

together.) Monoamine oxidase (MAO) inhibitors 

and amphetamines generally act to raise both 

norepinephrine and dopamine. 

A clinical trial reported in Psychosomatics in 2003 

by Olsen and colleagues randomized 20 patients with

CFS to receive either dexamphetamine or placebo 

and noticed statistically significant improvements in

fatigue. No improvements in physical function or pain

were seen. The sample size was so low that this study

was not powered to detect more subtle improvements

in the other domains. It was only intended to be and

was published as a pilot study to suggest that a larger

randomized control trial should be conducted to look

at dexamphetamine and its effects on fatigue and

physical function in people with CFS.

A study published a couple of years ago by Hickie’s

group in the Journal of Psychiatry randomized 

90 individuals to receive moclobemide, which is 

one of the new classes of MAO inhibitors that is 

not yet available in the United States. Traditionally,

MAO inhibitors have had many side effects, especially with respect to not being able to consume 

foods that include tyramine and leading to toxicity;

this new class of MAO inhibitors is not as problematic. This trial showed that, in individuals with

CFS, 51 percent of the subjects receiving the drug

improved versus 33 percent of those receiving 

placebo. The researchers noted that the improvements were in energy and vitality; improvements 

in mood and pain were not seen. The MAO 

inhibitor at this dose had neither antidepressive 

nor analgesic effects.

Milnacipran is approved in about 25 countries 

as an antidepressant. It is a mixed serotonergic 

noradrenergic reuptake inhibitor and it weakly 

antagonizes N-methyl-D-aspartate receptors, 

although it is not clear that that is related to its 

mechanism of action. Milnacipran has a profile 

close to amitriptyline with respect to being a 

mixed reuptake inhibitor. The company conducting the Milnacipran study also decided to look 

at novel outcome measures in fibromyalgia. They

posited that one of the reasons that many previous

studies in fibromyalgia had not succeeded was

because the outcomes had not been collected 

in the best way to show separation between 

drug and placebo.

In research on “ecological momentary assessments,”

instead of recording their symptoms in diaries, 

subjects wear a Palm-based or wristwatch-based

device that prompts them randomly over the course

of the day to record their pain, fatigue, and other

symptoms. This technology produces extremely 

rich data sets compared to the data obtained with

paper-and-pencil diaries, but it is expensive to collect data in this way. One of the reasons to use 

this new technology was discussed in a study published in the British Medical Journal by Stone and

colleagues showing that compliance with paperand-pencil diaries is abysmal. The subjects were 

asked to record the time they recorded their pain 

and pain level, and a microchip was installed in the

cover of each diary, unbeknownst to the subjects.

Even when Stone and his group gave subjects a 

90-minute window for margin of error, only 11 

percent of the diary entries could have occurred 

when the person said they occurred.

Subjects wear a Palm-based or 

wristwatch-based device that prompts

them randomly over the course of 

the day to record their pain, fatigue,

and other symptoms.

It has been known for a long time that people backward-fill diaries, but people also forward-fill diaries—

they anticipate what their symptoms will be before

their symptoms even occur. This is a real problem; 

the FDA is concerned about data integrity and has

been looking at these types of technologies when they

recommend going forward in different trials. This

device is somewhat annoying to wear, but produces

very good compliance with the diaries. Many researchers

are considering moving toward these kinds of assessments, rather than using paper-and-pencil assessments.

The Milnacipran trial randomized people to placebo,

once-a-day Milnacipran, or twice-a-day Milnacipran.

Similar to the Pregabalin study, the investigators

showed that the proportion of the subjects who had 

a 50 percent improvement in pain was about 37 

percent in those subjects who received twice-a-day

Milnacipran and 13 percent in the placebo group, 

a statistically significant result. Large differences 

in patient global improvement were also seen. 

The results were much better with either dose 

of Milnacipran than with the placebo.

100 Innovative Treatments in CFS
Innovative Treatments in CFS 101

One lesson learned in these studies is to enroll subjects with fibromyalgia or CFS who are in primary

care. Tertiary care patients have high levels of distress, high levels of mood disorders, high numbers 

of maladaptive illness behaviors, and multiple 

disability and compensation issues; they also are 

recalcitrant to therapy. At the other end of the 

spectrum, recruiting out of the general population

would include many people who are treatment-naive

and who would have a high placebo response rate.

Future studies of nonpharmacologic therapies should

address the relationship between the efficacy seen in

single-site trials and what was found in this single

large effectiveness trial. Phase II trials of pharmacologic therapies for CFS and fibromyalgia provide an

opportunity to innovate with respect both to study

design and outcome measures. Improvements seen

with various classes of antidepressants in conditions

like fibromyalgia and CFS are independent of whether

that person had a mood disorder at baseline. Whether

or not they respond to a tricyclic drug is not related

to whether they are depressed, whether their pain 

will get better, or whether their fatigue will lessen.

Discussion

Question: The one caveat in presenting the VA 

trial data is the abysmal compliance in the exercise

program. Less than 20 percent of subjects completed

the full gamut of exercises.

Dr. Clauw: The compliance rate is abysmal in any

study of exercise or CBT. If you get a 50 percent 

compliance rate in a CBT trial or an exercise trial,

you are doing well. It was abysmal, but it was not

much different than what is seen in other trials 

using CBT and exercise. However, the effect was 

quite a bit less.

Dr. Eldadah: Anecdotally, it has been said that 

Gulf War syndrome is more likely to occur not in

front-line soldiers or special operations soldiers, 

who are more intimately familiar with trauma 

and perhaps more likely to be risk-takers, but in 

support-type personnel. This finding raises the 

issue of expectation.

Dr. Clauw: That is somewhat true. The most consistent finding from the studies that have looked 

at Gulf War illness is that reservists were much 

more likely than active duty military to develop 

Gulf War illness. Some U.S. studies suggest that

women were more likely than men to develop it,

although that was not found in a United Kingdom

study. Gulf War illness did not selectively occur 

in people who were in the theater of operations.

People who left U.S. soil, even if they were far 

from the theater of operations, were equally 

likely to develop this constellation of symptoms 

and syndromes.

Improvements seen with various classes of antidepressants

in conditions like fibromyalgia and CFS are independent of

whether that person had a mood disorder at baseline.

Cognitive Behavioral Therapy 103

Cognitive behavioral therapy (CBT) has been

mentioned three times in the last 2 days in

relation to studies: Dr. White mentioned that

CBT was found to be effective in people with CFS,

Dr. Heitkemper stated that CBT was helpful in symptoms but not necessarily with the underlying mechanisms, and Dr. Clauw said that CBT helped increase

function in Gulf War veterans but was not as helpful

as exercise in alleviating the symptoms of fatigue and

pain. Many types of CBT rest on a common set of

theories. When evaluating whether CBT is effective,

we need to be clear about what type of CBT is 

being evaluated and for what outcome. 

CBT was developed as a therapeutic intervention 

for the mental illnesses and has strong empirical support for the treatment of depression and anxiety disorders.1 In the past 15 years, the principles of CBT

have been applied successfully to more traditional

medical conditions—usually chronic conditions such

as cardiovascular disease, cancer, diabetes, asthma,

and pain management.2-4 CBT encompasses the idea

that individuals can improve physical health or mental health through changes in thinking and behavior.

CBT is a blending of cognitive therapy and behavioral

therapy. Cognitive therapy focuses on the internal

mental environment of the individual. Issues commonly addressed are challenges to maladaptive beliefs

that individuals may have about their illness or about

their health. Cognitive therapy also examines maladaptive automatic thinking patterns and emotional

responses to illness. This form of therapy utilizes a

great deal of personal reflection and draws upon

insight to help individuals gain a clear understanding of their condition and the options that may be

available for managing the illnesses they face.

Behavioral therapy focuses on how the external 

environment affects individuals and on how 

learned behaviors can contribute to either the 

management or exacerbation of symptoms. 

Cognitive Behavioral Therapy

David A. Williams, Ph.D.
A number of well-established models of learning 

are included in behavioral therapies. Classical 

conditioning, operant conditioning, social modeling, and instructional learning are examples.

With classical conditioning, a neutral stimulus can

trigger a physiological response if it is paired with 

a natural trigger of that physiological response. 

For example, a bell paired with food will eventually

elicit salivation in a dog even when the food ceases 

to be present. Due to learning, the previously neutral

bell takes on the ability to elicit the physiological

response. Conditioning has been applied to some

degree in medical settings, to help diminish nausea

from chemotherapy and to supplement immunosuppressive agents.

Combining the techniques and principles

of cognitive and behavioral therapies

provides the tenets underlying the 

principles of cognitive behavioral therapy.

Another form of learning used in behavioral therapies

is operant conditioning, which utilizes either positive

or negative reinforcement to increase behaviors associated with improved health. For reinforcement to 

be effective, the desired behavior must occur on its

own or be shaped through approximation so that it

can begin to be reinforced. Once it occurs, it can be

increased through careful monitoring and reinforcement. For example, independent self-care or symptom management can be increased if families are

trained to watch for and reinforce efforts of patients

to function independently. 

Social modeling is based on the idea that an individual does not necessarily have to perform a behavior

in order to learn it. Individuals can observe other

people performing or behaving and can learn how to

mimic those behaviors even though those behaviors

have never been rehearsed. Examples include improving one’s own functioning by observing how others

in a support group have solved their barriers to

improved functioning.

Instructional learning encompasses the idea that

behaviors can be communicated verbally or through

written media; the individual who is supposed to 

perform the behavior may never observe the actual

behavior. Instructional learning is a common form of

therapeutics (that is, an educational intervention) but

there is no guarantee that someone who understands

the concepts concerning a behavior will ever actually

perform that behavior.

Combining the techniques and principles of cognitive

and behavioral therapies provides the tenets underlying the principles of CBT. Given that many different

principles constitute CBT, many versions of this form

of therapy can emerge.5

How might CBT be used in CFS? Versions of CBT

focus on sleep, physical functioning, mood, memory,

stress, and tension. When used rationally, the choice

of CBT techniques should target a specific problem.

Thus, when a form of CBT is chosen, it should follow

some hypothesis about the underlying mechanism

driving the illness. In the case of CFS, this presents 

a problem because the underlying mechanisms to be

targeted are not yet known. Many of the trials that

have used CBT have tried to hypothesize what mechanisms might be at play. Friedberg and Jason recently

published a review paper in which they proposed a

number of different models for understanding CFS.6

These models include an immune deficit model, a

sleep disturbance model, a neuroendocrine abnormality model, a predisposing personality model, 

and a symptom avoidance model. Because of the 

lack of consensus regarding the underlying mechanisms of CFS, CBT interventions to date are 

directed at managing overt symptoms. 

Most currently available forms of CBT for CFS have

been borrowed from successful applications in other

illnesses. Because there is no unified model, many

forms of CBT are tried with the hope that one of

them will make a difference. To date, little evidence 

of harm from this approach has been noted and 

there is some evidence of benefit in some people.

One strategy that might be used is to teach the 

relaxation response. The relaxation response has 

been used extensively in the field of chronic pain 

and insomnia. A JAMA paper in 1996 followed 

an NIH technology assessment panel that suggested 

that relaxation is a useful nonpharmacological intervention for pain and insomnia, both of which have

relevance to CFS.7 The relaxation response can be

taught in a variety of ways: progressive muscle relaxation, visual imagery, meditation, biofeedback, and

yoga. To date, no one method is superior to others,

but studies suggest that effective use of the relaxation response depends on the individual’s preference.

Thus, tailoring the intervention to the individual

104 Cognitive Behavioral Therapy 
allows the individual to use the method he or 

she finds most appropriate for achieving the 

relaxation response.

Another behavioral strategy is sleep hygiene, which 

is based on the idea that an individual can make

behavioral changes to bring about improvement 

in sleep.8 Timing strategies are an example. Individuals are encouraged to maintain a regular waking 

and retiring time so that the body can learn a regular

pattern for sleep. Patients are encouraged not to stay

in bed if they cannot fall asleep, and to get out of 

bed if they do not fall asleep within 15 minutes. 

This helps to prevent the bed from being associated

with struggle and discomfort. Thermal tips include

taking a warm bath or exercising several hours before going to bed and maintaining an environment

conducive to sleep, which is often a problem expressed

by individuals with CFS. Substances like caffeine 

and nicotine should be avoided as should stimulating television or reading material.

Stress management and assertiveness training represent another form of CBT.9 Over the course of time,

the types of stressors that humans face have shifted.

Historically, the stressors faced by humans were 

physical in nature and short lived. In the case of 

wild animals, hostile weather, plagues, and food

shortages, people either survived those stressors or

perished. After about 1900, threats from the physical

world diminished but threats from the social world

greatly increased. In modern times, many stressors 

are social stressors involving the work place, family

life, litigiousness, and government agencies. These

stressors do not kill us and therefore can exist and

wear on us for long periods of time. Due to the interpersonal nature of many modern stressors, assertiveness training can help individuals communicate more

effectively and form win–win relationships with others. In our work, assertiveness training has turned out

to be one of the most highly endorsed and satisfying

skills taught to patients with fibromyalgia. This form

of stress management has been very useful and is considered relevant to daily functioning and quality of

life, if not to direct symptom expression.

Cognitive reappraisal and structured problemsolving draws heavily from skills used in cognitive

therapy.10-12 While it may still be debated whether

emotions drive thinking or thinking drives emotions,

for the purposes of CBT it is useful to assume that

people learn automatic thoughts in response to certain situations; these automatic thoughts then drive

emotional responses. Inasmuch as these emotions 

are negative, symptoms can be made worse. The 

goal of cognitive reappraisal is to intervene at the

level of the automatic thought and alter the thinking process so that a fresh and potentially more 

adaptive set of emotional responses can emerge 

for common situations. The goal with this form 

of therapy is not to produce unrealistic bliss, but 

to challenge intense negative automatic thinking 

that might be blinding the individual to new and

potentially adaptive alternatives. 

Problem-solving is a useful form of therapy for individuals with chronic illnesses who tend to have more complex problems than the average individual. It is often

helpful to break these problems into solvable parts. 

A number of five- or six-step problem-solving processes exist in which individuals learn to break large

problems down into more manageable parts.13-14

Because of the lack of consensus

regarding the underlying mechanisms 

of CFS, CBT interventions to date are

directed at managing overt symptoms.

Another behavioral strategy is graded activation, 

also known as time-based pacing or activity-rest

scheduling.15-17 Individuals with a chronic condition like fibromyalgia or CFS will often engage in 

a destructive pattern of over-activity followed by

symptom flare-ups and the need for prolonged rest

and recovery. This latter period is often accompanied

by feelings of diminished self-worth and frustration

due to diminished productivity. When feeling better,

individuals again tend to overdo in an attempt to

“catch-up”; the result is often another flare-up, 

producing a cycle that is nonproductive. When

patients monitor their activity and rest periods 

over time, they discover that this cyclical pattern 

of activity results in shorter periods of productivity

and longer periods of recovery equaling less productive time during the day.

Many people think that task-based pacing is the 

solution to increasing function, but it is not. Taskbased pacing, which involves pacing one’s activities

based on completion of a task, can still result in 

overdoing; time-based pacing is more helpful. In 

time-based pacing an individual is active for a 

specific amount of time, which is then followed 

by a specific amount of rest, followed by another 

specific amount of activity based on time, and 

Cognitive Behavioral Therapy 105
followed by timed rest. This form of pacing is 

admittedly unnatural, and people have difficulty 

initiating this type of pacing; however, once they 

do, the number of flare-ups decreases and functional time rises. The goal of this strategy is to find the

safe amount of time an individual can engage in a

specific activity, which is where the individual must

start pacing. If the individual stops within this safe

amount of time and begins to rest, then the recovery

time will be much briefer since recovery will be tied

to a safe amount of activity rather than to a flare-up.

It might take a little longer to perform a given task 

by stopping and resting before it is done, but prevention of a flare-up means that other tasks can 

also be accomplished with less pain or fatigue. 

It may be difficult to initiate the use of time-based

pacing in the workplace; therefore, in therapy, individuals often start by pacing pleasant activities.18

Given that individuals with chronic illnesses like

fibromyalgia or CFS list the lack of pleasant activities as a problem, pleasant activity “scheduling” 

is another CBT skill that can be used to help 

manage symptoms and improve the quality of 

life of individuals with these conditions. 

What approaches work best? About 30 clinical 

studies have investigated CBT for fibromyalgia, 

but few can be considered well-conducted, randomized control trials. Few studies have used the same

combination of CBT skills, making comparison 

difficult among trials. The CBT literature for CFS 

is somewhat smaller and suffers from a similar lack

of uniformity; however, several CFS studies that followed a randomized control design hold promise. 

In one such study, 60 patients with CFS were randomly divided into two groups—a cognitive behavioral group and a standard care group. The types 

of CBT used were problem solving, graded activation, and cognitive restructuring, delivered in 16 

sessions. A 12-month outcome looked at improvements in physical functioning. Results showed that

73 percent of the subjects receiving CBT improved 

in physical functioning compared to only 27 percent of those receiving standard care. In the CBT

group, improvement was about 175 percent improvement over 12 months, and the number 

needed to treat was two in order to get one 

return to normal functioning.19

Another study compared graded activation and 

cognitive restructuring CBT with progressive muscle relaxation in 13 sessions over 4 to 6 months.

Improvements in physical functioning, fatigue, mood,

and global improvement were the outcomes. Results

showed that 70 percent of the CBT group improved

in physical functioning compared to 19 percent of the

relaxation-only group. In the CBT group, improvement was at 270 percent over 6 months, and the

number needed to treat was two in order to get 

one return to normal functioning.15

Another study found that CBT was better than 

a support group or a natural course. A total of 93

individuals were involved, using the CDC criteria,

and the groups were CBT, guided support group, 

and natural course. The types of CBT used were

graded activation, cognitive restructuring, and 

activity scheduling. This study comprised 13 sessions over 4 to 6 months, and the outcomes were

physical functioning, fatigue, and global patient

improvement. Results showed that physical functioning was improved and fatigue was lessened 

in the CBT group, and the support group and 

the natural course group had about equal outcomes. 

After 14 months in the CBT group, 49 percent of

subjects showed meaningful clinical improvement 

in physical functioning, 35 percent improved for

fatigue, and 50 percent improved on the global

impression of improvement.20

About 30 clinical studies have 

investigated CBT for fibromyalgia, but

few can be considered well-conducted,

randomized control trials.

One of the earlier studies was somewhat negative,

concluding that CBT was no different than immune

therapy. The groups were CBT, immune therapy, a

combination of CBT and immune therapy, and standard care. The form of CBT combined exercise and

cognitive restructuring, in only six 60-minute sessions

conducted over 2 weeks. The outcomes were global

health, physical functioning, and psychological 

functioning. Improvements were seen, but they 

were not specific to any single intervention.21

Summarizing the studies to date, the strongest 

evidence is for the use of graded activation and 

cognitive restructuring in CFS. There is moderate 

support for problem-solving, activity scheduling, 

and relaxation. The least support (because too 

few studies have been conducted) is for use of 

sleep hygiene, assertiveness, and a general stress 

106 Cognitive Behavioral Therapy 
management approach. Areas of additional research

needed include: explorations of CBT in mild forms 

of CFS, and effectiveness of specific forms of CBT 

for individuals with severe forms of CFS who may 

be unable to attend CBT sessions due to the severity

of their disease. Group CBT is understudied; most

studies have used a more traditional one-on-one 

format. CBT also should be studied in generalized

practice, as opposed to specialized practice. Most 

of the well-conducted studies so far have used an 

efficacy design in which a single site has been used.

The exception is the Prins et al. study that looked at 

13 therapists of varying quality; this study showed 

lower effectiveness than in other studies that used 

a single site and specialized clinics.

Future studies should further explore the use of CBT

techniques to manage symptoms, improve quality of

life, and eventually address underlying mechanisms 

of CFS as consensus builds on this issue. While CBT

to date cannot be considered a curative intervention,

it does appear to dramatically improve the condition

in a subset of individuals possessing the diagnoses 

of CFS or fibromyalgia.

Discussion

Question: What is the effect of CBT on beliefs such 

as interpersonal threats and anxiety, and also locus 

of control?

Dr. Williams: Beliefs such as locus of control are 

likely to be important in determining outcomes. 

We have a study in development that will look 

at locus of control, so I will hopefully be able to

answer this question more specifically in a year or 

so. There are some studies in FM and other chronic

pain conditions that have successfully enhanced 

internal locus of control with CBT. What we think

happens is this: individuals who successfully engage 

in activities, such as pacing or graded activation, learn

something about themselves (for example, they can

manage their condition while improving function);

those new achievements or new abilities to function

make it difficult to retain a belief in one’s inability 

to function. Thus, changes in behavior support

changes in beliefs. Simply telling folks to change 

how they think is not likely to be effective, but it 

is hard to argue with your own personal experience

that you are indeed doing better. In our attempts to

change beliefs, we usually try to set the stage for 

cognitive change by providing individuals with 

actual experiences where they are doing better.

Question: What about changing a belief such as 

disability? The person believes he/she is disabled. 

Was that one of the biggest potential problems of 

the Gulf War JAMA article?22

Dr. Williams: Disability was a major predictor of 

outcome. I do not know how we would try to change

a belief in disability, given that it is probably heavily

reinforced by so many environmental factors. As a

therapist you would need to have control over much

of the environment to make a meaningful change in

that belief, and this is not likely. It might be possible

to have people work to change their behaviors in

spite of the belief in disability, especially if they are

seeing an improvement in functioning. Compliance 

or adherence, however, is likely to be problematic

under these conditions.

Question: Regarding the pacing point, are the 

reasons behind that known? For instance, is it 

realistic compensation across people for the 

limitations from their condition, or is it certain 

personality types?

Dr. Williams: The problem with pacing is that 

when individuals are inactive they may have an

expectation of what they “should” be able to do—

this may be based on a previous history of being 

highly functional. Internally, there may be a drive 

to try to recapture the lifestyle before illness and 

its associated level of functioning. As people try 

to live as they used to, they may push their bodies 

to do things that it cannot do at the moment, 

causing an increase of symptoms and then a longer

period of time during which function is markedly

reduced. On a cognitive basis, there is a real disconnect between what the person wants to do 

(that is, what he or she thinks is possible) and 

what is actually possible. The motivation to feel 

unencumbered by illness (even for a short while) 

may override the knowledge that there will be a 

price to be paid for overdoing. 

References

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LE, Calhoun KS, Crist-Christoph P, et al. Update

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Cognitive Behavioral Therapy 107
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Peterson LE, Fordyce WE, et al. The effect of

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17. Gil KM, Ross SL, Keefe FJ. Behavioral treatment of chronic pain: four pain management 

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18. Lewinsohn PM. The behavioral study and 

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RM, Miller PM, editors. Progress in behavior

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19. Sharpe M, Hawton K, Simkin S, Surawy C,

Hackmann A, Klimes I, et al. Cognitive 

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LD, de Boo TM, Severens JL, et al. Cognitive

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22. Donta ST, Clauw DJ, Engel CC Jr, Guarino P,

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108 Cognitive Behavioral Therapy 

Summarizing the studies to date, the strongest evidence is for

the use of graded activation and cognitive restructuring in CFS.
The Food and Drug Administration (FDA) is

heavily invested in trying to understand the

issues associated with how to adjudicate 

outcomes in acute and chronic pain.

Chronic pain is a subjective event. Transference 

from an established and acute pain syndrome to

chronic pain is different for each person, and significant subjective issues are associated with the 

outcome. The FDA is interested in the implications 

of that transference and the syndromes associated

with chronic pain. It is likely that the exact cause 

of conversion to chronic pain is not the same in 

each circumstance, and therefore outcomes are 

more challenging. Chronic pain cannot be 

addressed without addressing acute pain.

It is only a belief system, and is not true, that the

FDA prevents the development of drugs by taking

“forever” to approve them. The amount of time it

takes to develop a new therapeutic intervention is

based on conducting the clinical trials that provide

the evidence that the new therapeutic product 

actually works. Much of the FDA’s work translates to the end product which, for physicians or

patients, is the therapeutic product. 

The end product for the FDA is the label associated

with the drug. The label has legal and regulatory 

uses, but the real purpose is to inform prescribers 

and patients about the documented benefits and 

risks of a product. The only place to obtain unbiased information about a product is the FDA label.

The components of the label are useful to practitioners and patients—results of clinical studies, 

how to use a particular agent, and what the agent 

is indicated for. The FDA does not regulate medical

care, but the indications do imply that the agent has

been studied. Contraindications to use, warnings,

precautions, adverse reactions, and dosage administration are included in the FDA label. FDA labels

will change shortly; the indications and usage will 

be placed first so people can open up the label and 

use it in an effective way instead of having to read

through a lot of verbiage.

The FDA evaluates the risks and benefits in the 

context of a population. It is hoped that people

become educated through the label and that the 

label provides the learned intermediary with the 

ability to evaluate the benefits and risks for a 

patient they advise. A patient may also be able 

to understand the information provided and to 

evaluate the benefits and risks in terms of their 

own values. Societal values are part of making 

a decision about therapeutic intervention. For 

example, thalidomide has just been approved in 

a restricted way for use in the United States; the 

societal machinations were significant prior to 

deciding that this agent deserves to be on the 

market for specific uses.

Transference from an established 

and acute pain syndrome to chronic

pain is different for each person,

and significant subjective issues 

are associated with the outcome.

Acute pain is a self-limiting condition that informs

how a drug for pain relief should be used, studied,

and labeled. Off-label use can result in serious adverse events, and perhaps even death. However, 

some therapeutic interventions warrant taking 

a certain risk relative to certain safety signals, 

depending on what the drugs are designed to do. 

If a patient is at risk because of an underlying 

disease and substantial benefit could accrue with 

Challenges in the Development of Acute and/or Chronic Pain Therapies 109

Challenges in the Development of Acute and/or 

Chronic Pain Therapies

Lee Simon, M.D.
a particular therapeutic product, the potential 

for benefit may warrant taking the associated 

risk, even though that risk may include a risk 

of death. Oral analgesics are used primarily in 

outpatient settings and parenteral analgesics are 

used for inpatient settings. While the nature of 

pain is subjective for each individual, the FDA 

is tasked with determining the meaning of pain 

relief in large population studies and whether a 

drug destined to be used acutely provides acute 

relief. For one person, acute relief might be 

defined as within 10 seconds; another person 

might define it as within 2 hours. The FDA 

standard is that an acute pain drug must 

have an onset within 60 minutes.

The FDA is interested in time to onset, peak effect,

effect size, and duration. Patients who take pain 

drugs would like to know that, for example, 80 percent of the subjects who were given the drug got 

pain relief within 1 hour, and the drug produced 

an 80 percent pain relief that lasted for 12 hours 

in 70 percent of the subjects. Unfortunately, that

specificity does not yet exist within the labeling 

environment at the FDA.

Nonsteroidal anti-inflammatory drugs are extraordinarily effective for dental pain; morphine is 

basically ineffective compared to 400 milligrams 

of ibuprofen in that model. However, in other 

models such as bunionectomy, 400 milligrams 

of ibuprofen does not have any effect and a 

patient-controlled analgesia pump is useful.

In single-dose studies of post-surgical abdominal,

gynecological, and orthopedic pain, 940 patients 

were given doses of one or two tablets. Drug X 

produced greater efficacy than placebo, and no

advantage was demonstrated for the two-tablet 

dose. For short-term (generally less than 10 days)

management of acute pain, the recommended dose 

of drug X is one tablet every 4 to 6 hours as necessary, and dosage should not exceed five tablets in 

a 24-hour period.

A more informative label might contain the following

attributes:

• “Initial pain benefit beginning at X minutes after

the first dose in a percentage of patients.” This

information would note the different models of

pain, which would give the provider a sense of

which drug and how much to prescribe.

• “Duration of pain relief is for X hours in 

a percentage of patients in Y model, and 

a second dose was required Z number of 

hours after the first dose in some patients 

in that model.”

The Merck Manual (17th edition, 2002) defines

chronic pain as pain persisting for greater than 

1 month beyond the acute injury, persistent or 

recurring pain for at least 3 months, and pain if

expected to continue or progress perhaps (but not

necessarily) associated with subsequent and ongoing

tissue injury. Chronic pain has no adaptive role, and

depression may follow as a consequence. Expectations of pain relief have to be tempered by how long

patients will survive with their illness, so the same

expectations cannot be held for cancer pain models

and noncancer pain models, for example. Studying

cancer pain models may be limited to 6 weeks of

experience, whereas in a chronic pain scenario, 6

weeks of experience is not particularly long.

Fibromyalgia is a real challenge. It is unknown

whether the pain is fibromyalgia or whether pain is

one manifestation of the disease called fibromyalgia.

Many data suggest that this might be a neuroendocrinologic disorder. 

There are many different ways to ask whether or 

not pain gets better. Objective measures exist, but

there is always a subjective component when measuring pain. In certain circumstances, other data are

needed to support the evidence that pain has changed.

To have a change in pain, there must be some evidence of a minimally clinically important difference,

but how to determine that difference is subjective. 

110 Challenges in the Development of Acute and/or Chronic Pain Therapies
In osteoarthritis, pain and function are highly 

correlated; in other scenarios, such as fibromyalgia,

they are not. The FDA is interested in understanding the central component of what it means for 

the patient to get better because buried within that

concept is a sense of the patient’s health-related 

quality of life. It is also possible that treating pain 

will make the patient worse; measuring the level 

of pain is difficult but is considered a critical outcome by the FDA. For example, in osteoarthritis,

when the knee is targeted, it is essential to ensure 

that other joints in the body do not worsen. In 

the context of rheumatoid arthritis, health-related 

quality-of-life measures are difficult to assess in

patients taking Methotrexate, because Methotrexate nauseates the patient when it is first taken.

Comparator drugs do better on a quality-of-life 

scale because they do not make patients nauseous.

Most clinical studies show that the majority of 

physicians have no clue how to measure outcomes.

Reporting that a patient is better is more related 

to ego than it is related to actual improvement.

Metrics for measurement of pain include healthrelated quality-of-life measures, the utility and 

use of rescue medications, the economics of the 

intervention, the presence of organ damage because of both the intervention and the causality 

of pain, the issue of suffering, and the issue of 

adverse events and what transpires because of 

the intervention.

Osteoarthritis can be used as an example of these

domains. The osteoarthritis domains enumerated 

by the Outcome Measures in Rheumatoid Arthritis

Clinical Trials (OMERACT, an international organization related to the World Health Organization) 

are similar to those adopted by the FDA for its 

primary outcomes: pain, function, and “patient 

global” for the signs and symptoms of osteoarthritis. (The domains are not related to the pain of

osteoarthritis; that indication does not exist.) The

function component of this outcome is defined 

by the Western Ontario and McMaster University Osteoarthritis Index as the result of asking 

24 questions about function, 2 about stiffness, 

and 5 about pain. A claim of improvement in

osteoarthritis is a claim of improvement in the 

signs and symptoms, measured by answers to 

questions related to pain, patient global, and 

the self-administered questionnaire for function. 

A proposed trial would be 3 months in length but

greater than 1 year after developing a structural

plane. Other areas to be evaluated during this trial

will include other joints, rescue medications, the

development of osteophytes if a structural plane 

is present, and the utility and use of devices. Pain 

and function will be analyzed separately, allowing 

for a better understanding of the disease state versus

the generalized pain state. In rheumatoid arthritis, 

the FDA uses a responder index called the American

College of Rheumatology/World Health Organization ILAR response index, which measures the tender

and swollen joints, and then measures three of the

following five: a scale for pain, patient global, physician global, health assessment questionnaire, and/or 

a sedimentation rate. The multimodality of rheumatoid arthritis, which also has pain as a component,

might make it more reflective of fibromyalgia than

would be a pain function global for a local disease

such as osteoarthritis.

To have a change in pain, there must 

be some evidence of a minimally 

clinically important difference, but 

how to determine that difference 

is subjective.

No product in the world, including water, is totally

safe and totally effective. Determining safety is made

even more complex because society has different ideas

about what is safe compared with what an individual

might believe. Measuring those differences and those

values is difficult; Europeans seem able to measure

these constructs more effectively than researchers 

and regulators in the United States. As the new 

world of molecular pharmacology evolves, society

will have to pay more attention to deciding some 

of these issues.

The goal is to create and recognize which drugs will

affect patient K differently than M and differently

than F. The subjective nature of pain will make a 

difference in how people experience the end result. 

It will be critical to develop a concept of minimally

clinically important differences that society and individual patients can accept. This concept will remove

the concern about numbers of patients in a trial, 

what an effect size might mean, and what the P-value

means. The FDA will not be able to accomplish that

alone; the implications for societal expectations are

Challenges in the Development of Acute and/or Chronic Pain Therapies 111
significant when considering what a $1 billion drug

might require and deliver, especially if the per-patient

cost of such a drug is $10,000 a year.

The ideal characteristics of a pain metric include 

that it should be easy to understand by patients 

and clinicians, because patients and clinicians conduct and participate in the studies and provide the 

answers to research questions. Truth in labeling

requires description of the clinical studies to the

providers and the subjects so they understand the

implications of the intervention. Measures also must

be applicable across studies to allow an understanding of the effect of a particular therapeutic. A pain

metric should define a clinically meaningful result, 

so it can be deemed a useful addition to pain control. “Clinically meaningful” must include a definition of the patient actually functioning better in

society as a result of the intervention. It has to be

valid in a variety of painful conditions, and it has 

to be achievable with the current medications. 

Rescue medications are used when a patient fails 

a therapeutic intervention trial. There may be synergism with rescue medications, and trials should be

designed to answer that question.

Another possible approach is in the context of a

mechanistic claim. Does a therapeutic product prevent wind-up? Does it alter N-methyl-D-aspartate

activity? Does it reduce prostaglandin levels such 

as in Cox 2 upregulation in the thalamus? Does it

treat acute neuropathic pain (which is different from

other kinds of pain)? Does it reduce nonsteroidal 

and opioid use? Mechanistic claims are popular 

for many industrial sponsors because they are 

easily measured.

At this stage for pain relief related to fibromyalgia, 

the important measures are known and can be incorporated into a clinical trial: improvement in measurable

pain, improvement in patient function, and improvement in “patient global.” Other measures might be

important as early markers of change that might predict, but are not anchored to, clinical improvement: 

a change in the hypothalamic-pituitary-adrenal axis

or a change in the neuroendocrine system, such as 

a hormonal change.

The FDA believes that trial length for fibromyalgia

should be 3 to 6 months, with at least a year of 

exposure for safety signals as defined by the International Harmonization Guidelines. Whether 6 or 

10 weeks is long enough is being debated regularly.

Other questions being asked by the FDA relating 

to fibromyalgia include:

• Should a patient have decreased symptoms, 

and for how long with and without therapy?

• Are fewer tender points, either by dolorimeter 

or otherwise, enough to suggest decreased pain?

• Is the fibromyalgia questionnaire, the FIQ, 

an adequate measure of function? Is it 

improvement in the pain of fibromyalgia 

or improvement in the disease?

• Would a cure be required, and what would 

be necessary to be considered a cure? 

At this stage for pain relief related to

fibromyalgia, the important measures 

are known and can be incorporated 

into a clinical trial: improvement in 

measurable pain, improvement in 

patient function, and improvement 

in “patient global.” 

Instead of improvement being measured by a 

lessening of the pain of fibromyalgia in this multisystemic disorder, improvement in fibromyalgia 

overall will be the standard, which will include 

the concept of improvement in pain.

The FDA web site provides information about all 

of these areas: www.fda.gov. Information about 

the Division of Analgesic, Anti-inflammatory, and

Ophthalmic Drug Products can be accessed from 

the FDA web site as well.

The current world of drugs is one of action and 

reaction, with drug exposure and drug experience.

Drug exposure issues are important, and have much

to do with informed consent issues in clinical trials

and post-marketing indications. Drug experience is 

an issue of benefit, weighing the risks such as adverse

events against the patient’s feeling and functioning

better and improvement in the underlying process 

or disease. The risks and benefits must be defined

accurately and must be evidence-based so the appropriate decisions can be made by and for patients.

112 Challenges in the Development of Acute and/or Chronic Pain Therapies
Challenges in the Development of Acute and/or Chronic Pain Therapies 113

Discussion

Dr. Krueger: Is there any movement within the 

FDA to consider the cost of therapy as one of the 

criteria that factor into drug approval?

Dr. Simon: Presently, the only places in the world

where a pharmacoeconomic outcome is required 

for approval are Canada and Australia, although

AMIA and the European community are moving 

in that direction. It is likely that economics will 

play an increasing role, not in approval but in 

effectiveness measures. The FDA is legislated by

Congress only to deal with efficacy, not effectiveness. Until Congress decides to change that issue, 

we do not have any legal authority to apply the 

issue of economics as an outcome.

Dr. Crofford: Have you given any thought to 

what kinds of outcomes or indices may be useful 

for a condition like CFS, where fatigue is even 

more subjective and more difficult to understand 

than pain?

Dr. Simon: At our last OMERACT meeting 

2 years ago, we invited patients for the first 

time to attend. About 35 patients attended; 

they were not all Australians. The patients 

informed us that physicians are interested in 

the context of rheumatoid arthritis and X-rays 

and the researchers are interested in the concept 

of function in osteoarthritis, but patients are 

really interested in fatigue. When you get doctors together, fatigue always gets thrown out 

because it is difficult to measure. We are going 

to have to grapple with fatigue as an outcome 

in all the inflammatory diseases. The reason is 

that patients care about fatigue and, fundamentally, we are developing drugs to make patients 

better—and patients tell us they want to be 

better in that way.

Dr. Crofford: In thinking about developing outcome measures for fibromyalgia, patients may 

tell you that fatigue is their most important 

symptom in even higher proportions than would

osteoarthritis and rheumatoid arthritis patients. 

Is there any thought by the FDA that fatigue 

might be reflective of function?

Dr. Simon: We have built into our discussions that 

the patient global included that kind of issue. A

patient global response has to be dependent on the

kind of question asked. Fatigue will be one of the

major topics of the workshop co-sponsored by the

FDA and the NIH scheduled for the fall of 2003, 

so fatigue will receive a tremendous amount of investigation and interest, and will be elevated into 

the real world of being part of the responder index.

Dr. Zubieta: We are trying to better understand

pathophysiologies of illness. We develop new technologies such as functional MRI, and we are able 

to measure receptors in the human brain. From 

the FDA’s perspective, to what degree would it 

be advantageous for drug companies to use these

types of measurements to define how well a drug 

is saved by a receptor site, or how well it correlates 

to a particular outcome measure?

Dr. Simon: From the regulatory perspective, we 

would be very interested in working with any 

sponsor to look at PK/PD understanding, predicting dose better, and all other early phenomena. 

To be able to use binding to a receptor as a clinical

outcome or as a surrogate for a clinical outcome is

not likely to be accomplished within my lifetime. 

We would like to foster that kind of investigation,

which we think can be useful as an early marker 

to understand how to predict pharmacodynamics.

Perhaps someday it may be useful in other ways, 

even in approvals, but not for a long time.

The themes of the discussions from 

this meeting can be grouped into two 

major categories: 

1. Who are chronic fatigue syndrome patients?

Some people lump everybody into one setting;

some people split CFS patients into different 

categories; and others categorize CFS patients 

as somewhere between the two extremes.

“Lumping” and “splitting” are concepts of 

categorization with which the field will have 

to grapple. Many “splitters” think that, in 

order to attain a uniform standard patient 

population, patient populations should be 

defined according to some biomarker or 

measurable phenotype that can be demonstrated, rather than symptoms that are 

sometimes difficult to interpret. Who should 

be studied when seeking to understand this 

disease: Populations? Clinical cohorts? 

Cross-sectional cohorts? Inception cohorts 

in the case of an acute illness? Patients or 

families? All of the above or none of the above?

2. What should be studied? The ultimate 

outcome from this meeting is the understanding that the brain is significantly more 

complicated than the liver and requires more

complicated measuring methods. Studying 

the brain requires precision in deciding what 

to study. For example, fatigue is a symptom 

of thyroid disease, but it is a symptom of 

both hypothyroidism and hyperthyroidism.

Certain CNS systems work in the same way.

Symptoms related to the CNS are plastic, and

dynamic variability is common. Measurements 

of liver function tests, for instance, usually produce results that are reproducible; the brain is

more complex, and it is necessary to control 

for quite a few more variables than is necesary

with more static systems.

The original question of this meeting was: Is the 

central nervous system a valid topic for study in

patients with CFS and related disorders? The consensus among most of the presenters appears to 

be: yes, it is a valid topic. For building models, 

the current question is why, and at what node, 

is the CNS an important study topic. For future 

directions, the key question is how to use the 

information presented in this concept that the 

CNS may be involved at single or multiple 

nodes along the development of symptoms 

that are related to CFS and other disorders.

The CNS Hypothesis in the Design of 

Future Studies

A model must incorporate the variability and 

clinical manifestations of CFS, including psychological distress, a variety of laboratory findings, 

the physical exam, and the presence or absence 

of overlapping conditions. A number of specific

symptoms appear to be very important in CFS, for

example, exercise intolerance, or post-exertional

fatigue. Female predominance has come up in discussion of irritable bowel syndrome, temporomandibular disease, fibromyalgia, and CFS. Familial 

clustering occurs in fibromyalgia, CFS, and other

fatiguing conditions. Another element that a useful

model of CFS must address is the altered perception

or belief state for some of the crucial symptoms of

CFS, such as exercise and cognition. Acute onset

reported by most patients, although not all patients,

must be addressed. It may be crucial to understand

what kinds of illnesses CFS patients do not get, because that knowledge can also be a key to defining

CFS and to developing models to understand CFS.

Methodological and Other Issues to Resolve

• CFS studies must be longitudinal and conducted in multiple centers with sufficient 

Optimal Directions for Research of the CNS in CFS 115

Session Six: Optimal Directions for Research of the CNS in CFS

Co-Chairs: Leslie J. Crofford, M.D., and Dedra Buchwald, M.D.

Summary of Discussion Sessions
subject numbers for statistical power and 

must be of sufficient duration to account 

for cycles of remittance and relapse.

• Methodological limitations, such as sampling 

time, specimen shipping conditions, processing methods and preservation, must also 

be standardized.

• Useful phenotypes for the symptoms of 

CFS must be developed and defined so 

they can be measured accurately.

• An animal model for CFS must be developed.

• Researchers should take advantage of the 

newer scientific methods and techniques that 

can be applied to provide immediate insights 

into the symptoms of CFS. Use of these

approaches will ensure that the projects 

undertaken are interdisciplinary.

• Unexplained clinical parameters include 

variability in clinical manifestations, specific

symptoms (for example, exercise intolerance),

female predominance, altered perception/belief,

correlates of acute onset, and exposures—medical histories remain vitally important as a key 

element in how to explain chronic diseases.

116 Optimal Directions for Research of the CNS in CFS

The original question of this meeting was: Is the central 

nervous system a valid topic for study in patients with chronic

fatigue syndrome and related disorders? The consensus among

most of the presenters appears to be: yes, it is a valid topic.
ORWH, Chair

Dr. Eleanor Hanna

Associate Director for

Special Projects and Centers

Office of Research on Women’s Health

Office of the Director

National Institutes of Health

Executive Plaza South

6120 Executive Blvd., Room 150A

Bethesda, MD 20892-7116

Phone: 301-435-1573

Fax: 301-402-0005

E-mail: eh43q@nih.gov

CSR

Dr. J. Terrell Hoffeld

Center for Scientific Review

National Institutes of Health

Rockledge 2 Building, Room 4116

6701 Rockledge Drive, MSC 7816

Bethesda, MD 20892-7816 (postal)

Bethesda, MD 20892-1813 (courier)

Phone: 301-435-1781

Fax: 301-480-2644

E-mail: th88q@nih.gov

NCCAM

Dr. Richard Nahin

Senior Advisor for Scientific Coordination 

and Research

National Center for Complementary and 

Alternative Medicine

National Institutes of Health

9000 Rockville Pike, MSC 2182

Bethesda, MD 20892-2182

Phone: 301-496-7801

Fax: 301-435-6549

E-mail: nahinr@mail.nih.gov

NCRR

Dr. John D. Harding

Health Scientist Administrator

Division of Comparative Medicine

National Center for Research Resources

National Institutes of Health

6701 Democracy Boulevard

Bethesda, MD 20892-4874 

(use “20817” for express service)

Phone: 301-435-0776

Fax: 301-480-3819

E-mail: hardingj@ncrr.nih.gov

NHLBI

Dr. Carl E. Hunt

Director

National Center on Sleep Disorders Research

National Heart, Lung, and Blood Institute

National Institutes of Health

Rockledge 2, Room 10-038

6701 Rockledge Drive, MSC 7920

Bethesda, MD 20892-7920

Phone: 301-435-0199

Fax: 301-480-3451

E-mail: HuntC@nhlbi.nih.gov

Dr. Stephen S. Goldman

Health Science Administrator

Division of Heart and Vascular Diseases

National Heart, Lung, and Blood Institute

National Institutes of Health

6701 Rockledge Drive, Suite 10193

MSC 7956

Bethesda, MD 20892-7956

Phone: 301-435-0560

Fax: 301-480-2858

E-mail: goldmans@nhlbi.nih.gov

Appendix 117

Appendix

Trans-NIH Working Group for Research on 

Chronic Fatigue Syndrome
NIAA

Dr. Denise Russo, Ph.D.

Division of Metabolism and Health Effects

National Institute on Alcohol Abuse

and Alcoholism

National Institutes of Health

5635 Fishers Lane, Room 2037

Bethesda, MD 20892-9304

Phone: 301-402-9403

Fax: 301-594-0673

E-mail: drusso@mail.nih.gov

NIAID

Dr. David M. Morens

Program Officer

National Institute of Allergy and

Infectious Diseases

National Institutes of Health

6610 Rockledge Drive, Room 4097

Bethesda, MD 20892-7630

Phone: 301-496-7453

Fax: 301-480-1594

E-mail: DMORENS@niaid.nih.gov

NIAMS

Dr. Deborah N. Ader

Program Director

Behavioral and Prevention Research

National Institute of Arthritis and

Musculoskeletal and Skin Diseases

National Institutes of Health

Building 45, Room 5AS-19H

45 Center Drive, MSC 6500

Bethesda, MD 20892

Phone: 301-594-5032

Fax: 301-480-4543

E-mail: aderd@mail.nih.gov

Dr. Susanna Serrate-Sztein

Director

Rheumatic Diseases Branch

National Institute of Arthritis and

Musculoskeletal and Skin Diseases

National Institutes of Health

Building 45, Room 5AS-37J

45 Center Drive, MSC 6500

Bethesda, MD 20892

Phone: 301-594-5032

Fax: 301-480-4543

E-mail: ss86e@nih.gov

NICHD

Dr. Lynne M. Haverkos

Director

Behavioral Pediatrics and Health

Promotion Research Program

National Institute of Child Health and

Human Development

National Institutes of Health

6100 Executive Boulevard, MSC 7510

Room 4B05B

Bethesda, MD 20892-7510

Phone: 301-435-6881

Fax: 301-480-7773

E-mail: haverkol@mail.nih.gov

Dr. Louis Quatrano

Program Director

National Center for Medical Rehabilitation

Research

National Institute of Child Health and

Human Development

National Institutes of Health

6100 Executive Boulevard, Room 2A01

Bethesda, MD 20892

Phone: 301-402-4221

Fax: 301-496-0832

E-mail: q2n@nih.gov

NIEHS

Dr. Anne P. Sassaman

Director

Division of Extramural Research and Training

National Institute of Environmental

Health Sciences

National Institutes of Health

MD EC-20

P.O. Box 12233

Research Triangle Park, NC 27709

Phone: 919-541-7723

Fax: 919-541-2843

E-mail: sassaman@niehs.nih.gov

Dr. Annette Kirshner

Program Administrator

National Institute of Environmental

Health Sciences

MD EC-23

P.O. Box 12233

Research Triangle Park, NC 27709

Phone: 919-541-0488

Fax: 919-541-5064

E-mail: ak27b@nih.gov

118 Appendix
NIMH

Dr. Peter Muehrer

Chief

Health and Behavioral Science

Research Branch

National Institute of Mental Health

National Institutes of Health

NIH Neuroscience Center, Room 6189

6001 Executive Boulevard, MSC 9615

Bethesda, MD 20892-9615

Phone: 301-443-4708

Fax: 301-480-4415

E-mail: pmuehrer@mail.nih.gov

Dr. Matthew V. Rudorfer

Associate Director for Treatment

Research, DSIR

National Institute of Mental Health

National Institutes of Health

NIH Neuroscience Center, Room 7163

6001 Executive Boulevard, MSC 7163

Bethesda, MD 20892-9635

Phone: 301-443-1111

Fax: 301-443-4045

E-mail: mrudorfer@nih.gov

NINDS

Dr. Linda Porter

Program Director

National Institute of Neurological

Disorders and Stroke

National Institutes of Health

NSC, Room 2113

6001 Executive Boulevard

Rockville, MD 20892

Phone: 301-496-9964

Fax: 301-402-2060

E-mail: porterl@ninds.nih.gov

NINR

Dr. Martha L. Hare

Program Director

Office of Extramural Research Programs

National Institute for Nursing Research

National Institutes of Health

One Democracy Plaza, Room 710

6701 Democracy Boulevard

Bethesda, MD 20892-4870

Phone: 301-451-3874

Fax: 301-480-8260

E-mail: harem@mail.nih.gov

OBSSR

Dr. Barbara DeVinney

Office of the Director

Office of Behavioral and Social Sciences

Research

National Institutes of Health

Building 1, Room 256

1 Center Drive

Bethesda, MD 20892

Phone: 301-402-3930

Fax: 301-402-7555

E-mail: Devinneb@od.nih.gov

ODS

Dr. Rebecca B. Costello

Deputy Director

Office of Dietary Supplements

National Institutes of Health

6100 Executive Boulevard

Room 3B01, MSC 7517

Bethesda, MD 20892-7517

Phone: 301-435-2920

Fax: 301-480-1845

E-mail: CostellB@od.nih.gov

ORWH

Ms. Joyce Rudick

Director of Programs and Management

Office of Research on Women’s Health

Office of the Director

National Institutes of Health

Building 1, Room 201

1 Center Drive

Bethesda, MD 20892

Phone: 301-402-1770

Fax: 301-402-1798

E-mail: rudickj@od.nih.gov

Appendix 119