Neuroimaging 

and Mental Illness: 

A Window Into the Brain 

Frequently asked questions about brain scans 

NATIONAL INSTITUTE OF MENTAL HEALTH 

U.S. Department of Health 

and Human Services 

National Institutes of Health 
2 

Brain imaging scans, also called neuroimaging scans, 

are being used more and more to help detect and 

diagnose a number of medical disorders and illnesses. 

Currently, the main use of brain scans for mental disorders is in research studies to learn more about the disorders. Brain scans alone cannot be used to diagnose a 

mental disorder, such as autism, anxiety, depression, 

schizophrenia, or bipolar disorder. 

In some cases, a brain scan might be used to rule out 

other medical illnesses, such as a tumor, that could 

cause symptoms similar to a mental disorder, such as 

depression. Other types of tests are needed for a mental 

illness to be properly diagnosed. Scientists are studying 

differences in the brains of people with and without a 

mental illness to learn more about these disorders. However, at this time relying on brain scans alone cannot 

accurately diagnose a mental illness or tell you your risk 

of getting a mental illness in the future. 

Some types of brain scans pose health risks due to the 

radiation they use to create a picture of the brain. 

Because of these risks, brain scans should not be used if 

you don’t need them. In addition, these scans are very 

expensive, and unless your doctor prescribes such a 

test, they may not be fully covered by health insurance. 

What Brain Scans Can Do 

Show damage to brain tissue, the skull, or blood 

vessels in the brain 

Be used with other medical tests to help doctors fi nd 

the right diagnosis for mood and behavioral 

problems 

Help researchers study healthy brain development, 

effects of mental illnesses or effects of mental health 

treatments on the brain. 

What Brain Scans Cannot Do 

Diagnose mental illness when used by themselves 

Predict risk of getting a mental illness. 
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Q.	 Can a brain scan tell me what mental 

disorders I have or might get? 

A.	 No scientifi c studies to date have shown that a 

brain scan by itself can be used for diagnosing 

a mental illness or to learn about a person’s 

risk for disease. Researchers use brain scans 

to study brain development in healthy people 

and people with illnesses, disease progression, and the effects of medications or other 

treatments on the brain. 

In practice, when used with other types of 

medical tests and done by an experienced 

doctor, brain scans can be used to confi rm a 

diagnosis of a small number of disorders, 

such as brain tumors, where there is obvious 

damage in the brain. Brain scans are not 

usually the fi rst test a doctor would do to 

diagnose changes in mood and behavior. 

Other medical tests a doctor may use include 

behavioral and cognitive tests or a medical 

interview. 

Q. Should I have a brain imaging scan? 

A.	 When used with other medical tests, they 

can provide useful information about: 

Brain tumors, infections, and other brain 

diseases 

Bleeding, blood clots, or other signs of stroke 

Skull fractures or brain damage from head 

injuries 

Diseases or disorders affecting the skull or 

blood vessels in the brain. 

Researcher analyzes FMRI brain images. 
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Patient enters PET scan machine. 

Q.	 What types of brain scans, or 

neuroimaging tests, are there? 

A.	 There are two main types of neuroimaging 

tests: structural and functional. 

Structural imaging creates a “snapshot” of 

the brain’s structure, including bone, tissue, 

blood vessels, tumors, infection, damage, or 

bleeding such as from a stroke. 

Functional imaging reveals the brain’s everchanging activity and chemistry by measuring the rate of blood fl ow, chemical activity, 

and electrical impulses in the brain during 

specifi c tasks. 

Q.	 Are there risks associated with brain 

scans? 

A.	 Brain scans are relatively safe and do not 

cause any pain. However, risks include exposure to magnetic fi elds and radiation. Safety 

measures are used to limit these risks such as 

using the lowest possible radiation or 

magnetic level to do the scan. 

Children and teens may be more sensitive to 

these risks. If your child needs a brain scan, 

ask if there are special precautions you can 

take or whether a different type of brain scan 

can be used. Ask the doctor doing the scan if 

the machine’s settings have been adjusted for 

a child. 

Women who are pregnant or breastfeeding 

should also talk with their doctor about how to 

prepare for any type of brain scan. While most 

types of scans pose little risk to the developing fetus, the doctor may make different recommendations to accommodate pregnancy. 

Another possible risk is claustrophobia, or a 

fear of small spaces. Many brain scanning 

machines look like large tubes or giant 

“donuts” that are open on both ends. The 

machines can be very loud while scanning 

takes place. Some people feel scared or nervous when inside the machines. Sometimes, 

Patient in MEG scanner. 
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an injury or other medical condition can make 

it uncomfortable or painful for a person to 

hold a certain position. 

It is important to stay still in order to get a 

clear picture. Tell your doctor if you are afraid 

of being inside the brain scanning machine or 

think you cannot stay still for any other reason. The doctor can give you a sedative to 

help you lie still, or may suggest a different 

type of test entirely. 

Talk with your doctor to make sure 

you understand the possible risks and benefi ts 

before deciding to get a brain scan. In general, 

a person should not need more than one of 

the same type of brain scan. If a doctor recommends a brain scan that you’ve already 

done in the past, ask if you really need to get 

the test repeated. 

Q.	 What can research using brain 

imaging technologies tell us about 

disease risk? 

A.	 As they continue to learn more about how the 

healthy brain develops and which processes 

may contribute to specifi c diseases, scientists 

are building a more complete picture of how 

to detect which people are at risk of common 

diseases. 

This research also is helping to reveal biological pathways that guide thoughts and emotions, and how experiences, medications, or 

environmental substances affect the brain. 

Scientists can use this information to design 

better screening and prevention for specifi c 

disorders, and improve on the delivery and 

effectiveness of mental health treatments. 

Technician checks MRI machine. 
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Risk from magnetic fi elds:* 

* Magnetoencephalography (MEG) scanning does 

not carry these risks because it does not use 

magnets. 

Magnetic resonance imaging (MRI) 

Functional magnetic resonance
 

imaging (FMRI)
 

Magnetic resonance spectroscopy 

(MRS) 

These scans use strong magnets to develop 

pictures of the brain. This means that a person 

must remove all jewelry, piercings, and clothing 

with metal before entering the scanning 

machine. 

Medication patches, such as nicotine patches or 

ones that release hormones, sometimes contain 

metal in the sticky backing, which can burn the 

skin if worn during an MRI. If you use such 

patches, talk to your doctor about if and when 

you should remove them. 

It’s important to tell your doctor if you have any 

metal in your body, such as metal braces or 

metal fi llings in your teeth, embedded bullets, 

shrapnel, or implanted medical devices – 

pacemakers, aneurysm clips, medication 

pumps, metal plates, screws, or pins. 

If located close to the head, they may distort the 

scanned image. Sometimes, the strong magnetic field causes these objects to move, which 

can cause an injury. If you’re not sure about your 

risk, check with the doctor before getting this 

type of brain scan. 

Risk from radiation: 

Computed tomography (CT) or 

computed axial tomography (CAT) 

Positron emission tomography (PET) 

Single positron emission computed 

tomography (SPECT) 

These scans expose people to low levels of 

radiation. For example, the amount of radiation 

from one CT scan of the head is about the same 

as the amount that the average person receives 

from natural sources of radiation over eight 

months.1

1

Computed Tomography (CT) – Head. http://www. 

radiologyinfo.org/en/info.cfm?pg=headct. Accessed 

on June 18, 2008. 

 Natural sources of radiation include 

naturally occurring radioactive materials and 

cosmic rays such as emitted by the sun. 

Also, some people may be allergic to the chemicals, called contrast dyes or tracers, used to 

make sure brain structures show up in these 

types of scans. In some cases, these chemicals 

are radioactive but lose their potency fairly 

quickly. 

If you have ever had a bad reaction to a contrast 

dye or tracer, tell the doctor before you get the 

scan. In general, children should not have PET 

or SPECT scans. 
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For more detailed descriptions of the different types 

of brain scans and other tests used to diagnose brain 

disorders, see the booklet “Neurological Diagnostic 

Tests and Procedures,” distributed by the National 

Institute on Neurological Disorders and Stroke 

(http://www.ninds.nih.gov). 

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For more information about mental illness 

and neuroimaging 

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illustrative purposes only. 
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U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES 

National Institutes of Health 

National Institute of Mental Health 

NIH Publication No. 09-7460