Mental illnesses change the size of your brain, study shows

How do mental illnesses change brain volume?

Each 1,300 participants suffered from at least one of the following six mental conditions; depression, attention-deficit hyperactivity disorder, autism spectrum disorder, schizophrenia, obsessive-compulsive disorder, and bipolar disorder.

During the study, the researchers used a special statistical method to calculate the average brain size of a person concerning their age and sex. They compared the expected average brain measurement against the actual brain volumes of the study participants.

“We can quantify how much an individual person’s brain volume deviates from the expectations, much like the growth charts commonly used for height and weight in pediatrics,” said Alex Fornito, one of the researchers and a professor of psychology at Monash University.

However, some previous studies that used a similar approach failed to identify treatment targets because the volume of various brain regions differs significantly among individuals. Moreover, the results from such studies indicate that out of 100, only seven people with a similar mental condition show deviation in the same parts of their brains.

“This means that it is difficult to pinpoint treatment targets by focusing on group averages alone. It may also explain why people with the same diagnosis show wide variability in their symptom profiles and treatment outcomes,” Professor Fornito added.

Therefore, to better understand the connection between mental illnesses and brain size, the researchers examined further how the deviations in brain volume spread from one brain region to the other.

This analysis revealed that although changes in volume varied in different regions, there are some areas in the brain where the volume deviations aggregate because these particular areas served as points where two or more regions overlap or connect.

“It’s possible that this circuit-level overlap explains commonalities between people with the same diagnosis, such as, for example, why two people with schizophrenia generally have more symptoms in common than a person with schizophrenia and one with depression”.

This advanced approach allowed the researchers to study the changes caused by a particular mental illness in the brain volume of a participant across more than 1,000 different regions in their brain. For instance, their study reveals that depression can be treated by targeting some brain circuits located in the frontal part of the brain.

There is one big limitation though

The current study goes one step ahead of previous research and reveals the in-depth connection between mental illnesses and brain function. It also explains how conditions like schizophrenia or depression force some brain regions to change and how one such small change affects the entire brain network.

However, the researchers suggest that their approach can only be used to identify potential treatment targets, and therefore, it will not work for everyone but rather for a few individuals.

For example, the previous section mentions that depression can be treated by targeting brain circuits in the front part. “These circuits are commonly used as targets for non-invasive brain stimulation therapies, but our data suggest that they may only be effective targets for around 1/3 of people,” said Segal.

Hopefully, with further research, scientists will be able to single out highly effective treatment targets in the future using the same approach.

The study is published in the journal Nature Neuroscience.