Depression Brain Scan: What It Can Show

Updated August 27, 2020

Medically Reviewed By: Lori Jones, LMHC

Over 16 million American adults age 18 and older live with major depressive disorder, which equates to about 6.7% of the population. It’s the leading cause of disability in the United States for people from the age of 15 to the age of 45.


Clinicians have long relied on the Diagnostic and Statistical Manual (DSM) as a resource for helping them diagnose patients with depression. While the guidance in the DSM is clear and up to date, it’s somewhat subjective based on how well patients can communicate their symptoms to their provider and how well a provider can assess a patient based on their self-reporting.

Researchers have done numerous studies on depression to help them better understand the types of treatment programs that will best help people with depression. In recent news, researchers have made advances in brain scanning to help them identify changes in the brain that contribute to depression. PET scans and MRI scans may help clinicians to detect specific characteristics in the brain structure or brain activity that relates to depression. The hope is that brain scans will lead to earlier diagnoses and more effective treatments for depression.

Using A PET Scan To Detect Depression

In a perfect world, doctors could peek inside the brains of people with depression and see what’s causing it. Obviously, that’s not possible, but it is possible to use a brain scan to see some of the changes that are going on in the brain.

One of the types of brain scans that a clinician might use is a PET scan. PET is an acronym for positron emission tomography. A PET scan is an imaging process that indicates how your tissues and organs are working. Doctors sometimes use PET images in conjunction with CT or MRI scans to get a clearer picture of the areas they’re studying for people with depression.

The way that it works is that a radioactive drug travels through your body and collects in areas of the body that have higher levels of chemical activity, which often indicates areas of diseases. Areas of unusual activity show up on PET scans have helped detect brain disorders, some varieties of cancer, and heart disease. PET brain scans sometimes show areas of disease before it shows up on other types of brain scans.


The radioactive drug tracer can enter the body by inhaling it, swallowing it, or by injecting it directly into the body, depending on which organ or tissue needs to be examined.

While PET scans may provide useful information to doctors, they present some risks that may not be worth taking. The drug tracer contains a small amount of radiation. The risk of negative effects is relatively low; however, the radiation may cause an extreme allergic reaction in some rare incidents. Radiation, even in a small amount, can be harmful in women that are pregnant or nursing.

The results of PET scans go to radiologists who will interpret the brain scans and report the results to your treating physician. Radiologists may use the results from PET scans to compare them with other tests like CT scans or MRI scans and may combine the results to provide the clearest picture of your condition.

Using An MRI Scan To Detect Depression

Advances in medicine have produced new types of MRI scans that reveal features of depression in the brain. One of the brain scans shows differences in the blood-brain barrier (BBB). The other MRI brain scan brings out differences in the complex network of the brain’s connections.

Kenneth T. Wengler, Ph.D., is a researcher at Columbia University in New York who has been doing research to better understand the complexities involved with the connections between the brain and depression. He is concerned about the high rates of relapse and recurrence with the current treatments for major depressive disorder. He was the first clinician to study the links between major depressive disorder and the blood-brain barrier (BBB). The BBB protects our brains from foreign substances in the blood that could injure the brain. It also protects the brain from hormones and neurotransmitters in the rest of the body to maintain aa constant environment for the brain. The BBB has a unique structure that allows the brain’s blood vessels to control the movement of molecules and cells between them and other bodily tissues. The function of the BBB is to shield the brain from harmful toxins and pathogens that may be running through the bloodstream.

Working in collaboration with his colleagues, Wengler developed a new type of MRI that they named IDEALS, which is an acronym for intrinsic diffusivity encoding off arterial labeled spins. This type of MRI allows them to track how water moves across the BBB. Wengler and his team used IDEALS in a study of 14 individuals living with major depressive disorder and 14 healthy control participants.

The results of the study showed that the participants with the major depressive disorder had a reduced capacity for water permeability in their BBBs. Essentially, for the people with depressive disorder, the water was not as able to move from their blood vessels into brain tissue. The water moved more freely in the participants that were part of the healthy controls. Wengler and his team also reported that the difference in the permeability of the water was notable in the amygdala and hippocampus regions of the brain. Previous research studies in brain imaging have also shown that these two regions of the brain are essential in understanding the working of the brain related to major depressive disorder. Wengler states that they were able to observe changes in the BBB in gray matter areas of the brain that they knew would be altered in people that have a major depressive disorder.


In his second study using MRI imaging, Wengler explored disruptions to something that scientists call the connectome, which they explain as the “complete, point-to-point spatial connectivity of neural pathways in the brain.” Wengler’s study is new in that prior studies focused on the connectivity between various regions of the brain as they relate to major depressive disorder. This new study builds on the past research of Guoshi Li, Ph.D., a researcher from Image Display, Enhancement, and Analysis Group from the University of North Carolina School of Medicine in Chapel Hill, NC.

Li and his team used a new tool called a multiscale neural model inversion framework in conjunction with a functional MRI (fMRI), where they conducted a study that included 66 adults living with major depressive disorder and 66 healthy control participants.

In his study, Li and his colleagues were able to look at the activity in microscopic circuits as they relate to large-scale brain activity. Li explains that healthy brains work best when they have a balance between excitation and inhibition, so they assessed the functions of excitation and inhibition among the circuits of the brain cells. The results of the functional MRI scans showed that people with major depressive disorder had different patterns of excitation and inhibition in the dorsal lateral prefrontal cortex, as compared with the participants in the study that didn’t have a major depressive disorder. The dorsal lateral prefrontal cortex helps to regulate the amygdala in the brain. This is an important concept because scientists believe that the symptoms of depression can surface when the brain doesn’t inhibit the amygdala appropriately.

This discovery shows that the dorsal lateral prefrontal cortex is an area in the brain that helps to adjust self-control and emotions. Li’s study indicates that excitation and inhibition were reduced in patients with major depressive disorder, which affected the control of their executive function and emotional regulation. Proper executive function is important because it helps us to plan, focus, remember things, and multi-task. Li adds that his study shows that the control functions in major depressive disorder are impaired, which could lead to a rise in the responses from the amygdala. The result of this will generally increase a person’s anxiety or other negative moods.

Li’s study also showed that the thalamus, which is another part of the brain that’s involved in emotional regulation, tended to show higher recurrent excitation in people living with major depressive disorder. Up until the completion of the studies that were performed by Wengler and Li, all that scientists had was a superficial understanding of the connections in the brain. Li explains that his study allowed him to identify the disconnections within various regions in the brain. Brain scans are a powerful tool for researchers to study brain disorders, which could pave the way for more effective diagnoses and treatment of major depressive disorders.


The exciting thing about the research that’s being done on the brain related to major depressive disorder is that the researchers are learning more about how the brain works all the time. Advances in brain research will lead to the development of new and effective treatments for depression in the future. In the interim, no one needs to suffer from a major depressive disorder. Whether your symptoms are mild or severe, you can get help by contacting a licensed therapist.

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