What 1,000 brains told researchers about mental illness

Key points:

• Researchers from Monash University mapped nearly 1,300 brains of people diagnosed with mental illness

• The six different types of mental illness assessed by the Turner Institute for Brain and Mental Health and School of Psychological Sciences were: schizophrenia, depression, bipolar disorder, obsessive-compulsive disorder, attention-deficit hyperactivity disorder or autism spectrum disorder

• No more than seven percent of people with the same diagnosis showed a major deviation in the same brain area

A team of Monash University researchers mapped the brains of nearly 1,300 people living with one of six kinds of mental illness. The team mapped over 1,000 regions of each brain to assess size and volume to determine deviation in scale.

PhD student Ashlea Segal, a part of the team leading research, said existing research on the relationship between brain size and a diagnosed mental illness was not indicative of a person’s specific circumstances.

Researchers used a person’s age and sex to determine the expected brain volume and gauge whether there were large deviations. Then, looked at how those deviations were impacted by the brain’s connectivity.

“Because the brain is a network, dysfunction in one area can spread to affect other, connected sites. We found that, while deviations occurred in distinct brain regions across different people, they were often connected to common upstream or downstream areas, meaning they aggregated within the same brain circuits,” Ms Segal explained.

“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.

“Over the past few decades, researchers have mapped brain areas showing reduced volume in people diagnosed with a wide variety of mental illnesses, but this work has largely focused on group averages, which makes it difficult to understand what is happening in the brains of individual people.”

Ms Segel likened a person with mental illness’ brain volume to someone’s height, to drive the point home about general statistics and their application.

“For example, knowing that the average height of the Australian population is about 1.7 metres tells me very little about the height of my next-door neighbour.”

The research team lead Professor Alex Fornito stated that the study was made possible through new data gathering methods, developed by Professor Andre Marquand at the Donders Institute, Netherlands, who co-led the project.

“We used a statistical model to establish expectations about brain size given someone’s age and sex. We can then quantify how much an individual person’s brain volume deviates from these expectations, much like the growth charts commonly used for height and weight in paediatrics,” said Professor Fornito.

“We confirmed earlier findings that the specific brain regions showing large deviations in brain volume vary a lot across individuals, with no more than 7 percent of people with the same diagnosis showing a major deviation in the same brain area.

“This result means that it is difficult to pinpoint treatment targets or causal mechanisms 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.”

Research findings have opened up the door to future studies and potential treatment options for people with specific subsets of mental illness — specifically, depression, which was related to frontal area connectivity.

“The framework we have developed allows us to understand the diversity of brain changes in people with mental illness at different levels, from individual regions through to more widespread brain circuits and networks, offering a deeper insight into how the brain is affected in individual people,” Professor Fornito concluded.

To read the study please visit Nature Neuroscience and if you or someone you love is at risk of struggling with mental health, please get in touch with available support:

Beyond Blue — 1300 22 4636

Mental Health Emergency — 13 14 65

Lifeline — 13 11 14