Single-Arm Feasibility Study of Exposure-Based Treatment for Undifferentiated Somatic Symptom Disorder
Phase: NA
Conditions: Somatic Symptom Disorder
Sponsor: Karolinska Institutet

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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[Translated from the original that was approved by the Swedish ethical review authority] 
 
 
 
 
 
 
 
 
 
Study protocol 
Exposure-based treatment for undifferentiated somatic symptom disorder  
ClinicalTrials.gov identifier: NCT04511286 
 
 
Note that due to the feasibility nature of this clinical trial, there was no statistical analysis plan 
over and above the rudimentary a priori guidelines for interpretation listed in Table 1. 
 
 
Approved by the Swedish ethical review authority on May 20th 2020. 
Translated to English on July 19th 2021. 
 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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[Translated from the original that was approved by the Swedish ethical review authority] 
 
Study protocol 
 
Exposure-based treatment for undifferentiated somatic symptom disorder: 
a feasibility study 
 
Summary 
A substantial proportion of patients in the health care system are bothered by a recurrent 
preoccupation with physical symptoms. Whenever this preoccupation becomes clinically 
significant in terms of cognitions, emotions or behaviour and cannot be explained by the 
common anxiety or mood disorders, the criteria for DSM-5 somatic symptom disorder are 
likely to be met. Exposure-based psychological treatment where the patient systematically 
seeks out situations that give rise to symptoms and related discomfort have been found to 
have meaningful effects on subjective somatic symptom burden and mood in several forms of 
preoccupation with physical symptoms, but is rarely offered in routine care, probably partially 
because existing treatment protocols have been developed for specific somatic symptom 
clusters (e.g., fibromyalgia) or specific forms of preoccupation with symptoms (e.g., the fear 
of having or developing a severe disease). The aim of this study is to investigate the feasibility 
of offering exposure treatment for somatic symptom disorder without selecting patients based 
on their specific somatic symptoms or most pronounced emotional reaction to somatic 
symptoms. Instead, the treatment is expected to be suitable for many types of preoccupation 
with symptoms, and many forms of physical symptoms, which potentially makes the protocol 
relevant for a wider target group. A within-group feasibility trial is conducted at Karolinska 
Institutet, where 40 participants with somatic symptom disorder are enrolled in psychological 
treatment for 8 weeks. The outcome of the study focuses on various aspects of feasibility. 
Overview of the field (background) 
One fifth of primary care patients, and approximately 37-66 percent of specialist care patients, 
seek care for symptoms without a clear medical explanation (1-3). Many of these patients are 
diagnosed with a functional somatic syndrome; a diagnosis primarily based on the presence of 
physical symptoms such as fibromyalgia in rheumatology or irritable bowel syndrome in 
gastroenterology (4). Such conditions commonly lead to considerable suffering and functional 
impairment (5, 6), and put substantial strain on the health care system (7). Pharmacological 
therapies, typically antidepressants and symptom-specific medications, often do not provide 
adequate relief (8). 
Somatic symptom disorder is a diagnosis characterised by a clinically significant pattern of 
negative interpretations, anxiety or excessive health behaviours in relation to somatic 
symptoms. This type of preoccupation with symptoms affects the experience and intensity of 
a large number of physical symptoms, both with and without a clearly defined medical 
genesis (9). For example, in pain, the fear and preoccupation with pain has been found to have 
a higher predictive value for chronicity than pain itself (10). Behaviours that serve to evaluate 
somatic symptoms, seek information about symptoms and avoid symptom-related discomfort 
often contribute to impaired functioning and worsened symptoms in the long term (11-13). 
In exposure-based treatment, the patient is encouraged to reduce his or her preoccupation with 
somatic symptoms by systematically seeking out and approaching situations and phenomena 
that give rise to unwanted somatic symptoms or symptom-related discomfort. The treatment is 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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[Translated from the original that was approved by the Swedish ethical review authority] 
tailored for the needs of the patient as based on functional analysis. This type of treatment has 
been found to be efficacious in several functional somatic syndromes, such as fibromyalgia 
and irritable bowel syndrome (14, 15), as well as in specific types of symptom preoccupation 
such as health anxiety and anxiety sensitivity (16, 17). In clinical trials where patients have 
been recruited based on a specific syndrome or class of somatic symptoms, the primary 
outcome has typically focused on subjective somatic burden, and within-group effects have 
been typically moderate to large.  
In Swedish healthcare, access to exposure-based treatment for somatic symptom disorder is 
poor. Only about every other primary care clinic reports being able to meet patients’ demand 
for mental health care (18), and primary care often lacks the necessary resources for offering 
specific psychological treatments for functional somatic syndromes and specific forms of 
preoccupation with somatic symptoms. A unified treatment protocol that could suit a wider 
spectrum of physical symptoms and types of preoccupation with somatic symptoms could 
potentially increase access to exposure-based treatment for somatic symptom disorder. 
However, it is yet unclear if one and the same exposure-based treatment could be rated as 
credible and be sufficiently effective for the heterogeneous group of individuals who seek 
care for somatic symptom disorder, regardless of symptom domain (e.g., fibromyalgia) or 
type of preoccupation with symptoms (e.g., health anxiety). 
Research question (study aims) 
The aim of this within-group study is to evaluate an exposure-based treatment for somatic 
symptom disorder in terms of credibility and feasibility (see Table 1). Secondary outcomes 
include preliminary within-group efficacy, where the expectation is at least a moderate effect 
(ca d=0.5) on subjective somatic symptom burden (see Table 2). 
Table 1. Dimensions of feasibility assessed within the study 
Feasibility aspect 
Outcome 
A priori rule of thumb for adequacy 
Distribution of somatic symptoms 
and preoccupation with symptoms 
See Table 2 
Exploratory, interpreted in the light of 
other aspects such as recruitment path 
(proportion of patients informed of the 
study by a health care provider) 
Treatment credibility 
Credibility/Expectancy scale 
(19) 
Mean of at least ca 30 points (equivalent 
to a mean of 6 on a scale from 0 to 10) 
Adherence to the protocol 
Number of completed 
modules 
 
Number of completed 
exposure exercises 
At least ca 60% of modules completed 
 
At least ca 50% of participants having 
worked actively with exposure (at least 2 
exposure exercises) 
Credible rationale for exposure 
Study-specific Likert-scale 
(mid- and post-treatment) 
[Note: This was only 
administered at post.] 
-  
Weekly measurements of somatic 
symptom burden and symptom 
preoccupation 
Number of measurements 
completed 
 
Perceived strain caused by 
measurement strategy 
Post-treatment data retention ca 70% 
 
At least 75% regard the strain to be 
acceptable [Note: Below 7 on a scale 
from 0 to 10, as decided on Nov 13th.] 
Satisfaction with the treatment 
Client Satisfaction 
Questionnaire (CSQ-8) 
 
Modified questionnaire from 
Swedish ethical review 
authority application 2019-
03317 [Note: Not 
CSQ-8 mean of at least ca 22 points 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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[Translated from the original that was approved by the Swedish ethical review authority] 
administered due to an 
administrative error.] 
Adverse events and negative 
experiences 
Adverse events 
questionnaire used in 
previous clinical trials (e.g., 
Regional ethics review 
board of Stockholm  
application 2014/1530-31), 
NEQ-20 
Exploratory, weighed against preliminary 
efficacy 
 
Description of the research project (methods) 
 
Design 
Observational study at Karolinska Institutet [Note: Stockholm, Sweden]. Frothy participants 
with somatic symptom disorder are recruited via information to primary care, the study web 
page and advertisements in social media, and are subsequently offered 8 weeks of exposure-
based treatment via the internet. Recruitment is scheduled to begin in mid-August 2020. 
Recruitment 
The target group is adult swedes with somatic symptom disorder who are interested in 
psychological treatment. Recruitment is conducted via information to health care clinics, the 
study webpage and social media advertisements. Individuals expressing interest in the study 
are referred to the study web page where they are encouraged to submit an application. The 
self-referral procedure ensures that these individuals are given time to reflect on their decision 
to apply for the study. At the time of application, the potential participant is immediately 
presented with the information necessary for informed consent. The voluntary nature of 
participation, routines for the management of data and the risks of participation are conveyed 
in a clear manner. Informed consent is provided via the web platform, which is a method used 
in previous clinical trials, see for example Regional ethics review board of Stockholm 
applications 2013/375-31/5 and 2014/1530-31. An interview with a licensed psychologist or 
trainee psychologist under the supervision of a licensed psychologist is conducted via 
telephone for the collection of routine clinical data and the assessment of eligibility criteria: 
a) DSM-5 somatic symptom disorder as assessed using the Health Preoccupation 
Diagnostic Interview (HPDI) (20), with at least 4 months of recurrent somatic 
symptoms 
b) The preoccupation with somatic symptoms is not better explained by another 
psychiatric disorder such as illness anxiety disorder, panic disorder or obsessive-
compulsive disorder 
c) The individual reports being interested in undergoing a focused psychological 
treatment for 8 weeks, to reduce the impact of bothering physical symptoms 
d) At least 18 years old 
e) Swedish citizen living in Sweden 
f) Can speak and read Swedish 
g) No severe psychiatric condition such as bipolar disorder, suicidal ideation or a 
psychotic disorder. This is based on the eligibility interview where the clinician 
administers the Mini-International Neuropsychiatric Interview (MINI) (21). 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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h) Not obvious medical risks associated with exposure-based treatment, and no somatic 
condition, or treatment for a somatic condition, is a significant obstacle for exposure-
based treatment. 
i) Continuous psychotropic medication (e.g., antidepressants, anticonvulsants, 
benzodiazepines, nonbenzodiazepines) and medication with opioids has been stable 
for the past 4 weeks and is expected to remain so during the intended treatment period. 
j) Not alcohol or substance use deemed a serious obstacle to taking part in therapy 
k) Not planned absence for more than one week of the intended treatment period 
l) Complete pre-treatment assessment 
Treatment 
Patients complete an 8-week exposure-based treatment. The treatment is a text-based guided 
self-help intervention provided via the internet (22), with five modules, equivalent to book 
chapters, with corresponding exercises alongside email-like communication with a therapist. 
The treatment manual, written by Erland Axelsson, is made freely available via the internet. 
The treatment is tailored to suit the unique needs of each patient. The introduction of the 
treatment (module 1) focuses primarily on education about how psychological factors can 
contribute to somatic symptoms and related problems. The patient begins to monitor his or her 
own behavioural patterns in relation to somatic symptoms and begins working with response 
prevention (23), that is, the reduction of behaviours aiming to reduce symptoms and related 
discomfort in the short term. During the following modules, the patient plans individually-
tailored exposure exercises that are expected to give rise to discomfort related to physical 
symptoms including unwanted thoughts. The treatment is delivered by a licensed psychologist 
or trainee psychologist under supervision. 
Measurements and psychometric instruments 
Measurements primarily rely on self-report questionnaires administered via a secure web 
platform (encrypted traffic and two-factor authentication). The study involves the following 
measurements: the screening (at application), the pre-treatment assessment (before week 1), 
weekly measurements during the treatment period (before week 2-8) and the post-treatment 
(after week 8). A follow-up assessment is also conducted 3 months after treatment. Automatic 
SMS reminders prompt participants to complete each measurement, and manual reminders are 
given via telephone if necessary, without conveying treatment content. Over and above 
routine clinical questions for example regarding sociodemographic variables (such as age, 
sex, educational attainment and civil status) the following questionnaires are administered via 
the internet: 
Table 2. Self-report questionnaires administered in the study 
Questionnaire 
Outcome 
Ref 
SN 
PRE 
W 
POST 
3MFU 
Patient Health 
Questionnaire-15 (PHQ-15) 
Somatic 
symptom 
burden 
(24) 
x 
x 
x 
x 
x 
Somatic Symptom Disorder-
B Criteria Scale (SSD-12) 
Symptom 
preoccupation 
(25) 
x 
x 
x 
x 
x 
Symptom Preoccupation 
Scale (SYMPS-prel) 
Symptom 
preoccupation 
Preliminary 
version 
x 
x 
x 
x 
x 
14-item Health Anxiety 
Inventory (HAI-14) 
Health anxiety 
(26) 
x 
x 
 
x 
x 
Anxiety Sensitivity Index 
(ASI) 
Anxiety 
sensitivity 
(27) 
x 
x 
 
x 
x 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
Study protocol intended for peer review 
 
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GAD-7 
Anxiety 
(general) 
(28) 
 
x 
 
x 
x 
Patient Health Questionnare 
(PHQ-9) a 
Depression 
(29) 
x 
x 
 
x 
x 
12-item WHO Disability 
Assessment Schedule 2.0 
(WHODAS 2.0) 
Functional 
impairment 
(30) 
x 
x 
 
x 
x 
Alcohol Use Disorders 
Identification Test (AUDIT) 
Alcohol use 
(31) 
x 
 
 
 
 
Drug Use Disorders 
Identification Test (DUDIT) 
Drug use 
(32) 
x 
 
 
 
 
Credibility/Expectancy scale 
(C/E scale) 
Credibility and 
expectancy 
(19) 
 
 
w. 3 
 
 
Working Alliance Inventory 
(WAI) 
Relationship 
with the 
therapist 
(33) 
 
 
w. 3 
 
 
Client satisfaction 
questionnaire (CSQ-8) 
Satisfaction 
with the 
treatment 
(34) 
 
 
 
x 
 
20-item Negative Effects 
Questionnaire (NEQ-20) 
Negative 
experiences 
(35) 
 
 
 
x 
 
3MFU = 3-months follow-up, PRE = pre-treatment, POST = post-treatment, SN = screening, W = weekly  
a) The suicidal ideation item is administered on a weekly basis. Patients with heightened scores are contacted 
and referred to routine care if deemed necessary. 
Data safety and management 
The study web platform employs encrypted traffic and two-factor authentication. Researchers 
in the project have access to study data, which is stored and managed in accordance with 
European Union and Swedish data protection and privacy legislation. Personal data are 
exclusively stored in systems classified and provided specifically for this purpose by 
Karolinska Institutet. Study results are reported in a manner that does not make it possible to 
identify individual participants. 
Time schedule and feasibility 
Recruitment for the study is scheduled to begin in August 2020. Eligibility interviews are 
conducted in September 2020, treatments span from October to December 2020 and a follow-
up assessment is conducted 3 months after treatment termination with some tolerance for late 
replies. Data collection is expected to end around May 2021. The processing of data is 
expected to be relatively swift, and a scientific manuscript is expected to be submitted for 
peer review around June 2021, thus probably reaching publication in the autumn of 2021. 
Researchers in the project have extensive experience of conducting clinical trials of 
psychological treatment via the internet, and in particular for groups similar to that studied in 
the present study – e.g., individuals with health anxiety and irritable bowel syndrome – and 
with similar recruitment strategies. The treatment evaluated in this research project is intended 
to meet a large and seemingly unmet need in the population, and the study has been approved 
by the head of the Department of clinical neuroscience at Karolinska Institutet, which speaks 
for the study being completed as planned. 
The research group 
The researchers have extensive experience of research in primary care and concerning 
psychological treatment for somatoform conditions, functional somatic syndromes and 
anxiety related to somatic conditions. Erland Axelsson, licensed psychologist and PhD at 
Karolinska Institutet, wrote his dissertation on the exposure-based treatment of health anxiety, 

Exposure-based treatment for undifferentiated somatic symptom disorder: a feasibility study 
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[Translated from the original that was approved by the Swedish ethical review authority] 
a form of preoccupation with symptoms, and has developed a diagnostic interview for the 
assessment of somatic symptom disorder. Erland has made contributions to several clinical 
trials of psychological treatment for conditions such as fibromyalgia, chronic stress disorders, 
pathological worry, depression and paroxysmal atrial fibrillation. Erland has documented 
experience of the development and evaluation of psychological treatments including study 
design, the implementation of research methods, the supervision of clinicians and the day-to-
day project management of clinical trials in primary care. Brjánn Ljótsson, licensed 
psychologist and PhD, associate professor, is a research group leader at Karolinska Institutet. 
Brjánn co-founded the Internet psychiatry unit of Region Stockholm and has led the 
development of several internationally recognised exposure-based protocols for individuals 
reporting distress related to somatic symptoms. Brjánn is a world-leading researcher in 
psychological treatment for functional somatic syndromes, specialising in irritable bowel 
syndrome and certain somatic conditions such as atrial fibrillation. Brjánn has also taken part 
in treatment research at Gustavsberg academic primary care clinic. Sandra af Winklerfelt 
Hammarberg licensed general practitioner and doctoral student at Karolinska Institutet is the 
head of Liljeholmen academic primary care clinic, Stockholm, Sweden. Sandra has extensive 
experience of clinical work in primary care and has expressed interest in supporting the 
project. Robert Johansson licenced psychologist and PhD, associate professor at Stockholm 
university, has extensive experience of clinical research focusing on anxiety and mood 
disorders. Robert is heading a research program for the development and evaluation of 
emotional awareness and expression therapy (EAET) for somatic symptom disorder. 
Significance 
A credible and promising exposure-based treatment for undifferentiated somatic symptom 
disorder could potentially lead to a significant improvement in the access to treatment for 
patients with somatic symptom disorder in primary care. If results are found to be promising, 
the next step could be to assess treatment efficacy more carefully, for example versus standard 
interventions (“usual care”) within the context of a randomised controlled trial in routine care.  
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