Mental Disorders | Vulnerability begins before birth

(Montreal) Factors that impact brain development during pregnancy may increase the risk of suffering from mental illness later in life, researchers at CHU Sainte-Justine have found.

Posted at 10:43 a.m.

Jean-Benoit Legault
The Canadian Press

In work carried out in collaboration with the ENIGMA Consortium and involving dozens of researchers around the world, Professor Tomas Paus and doctoral student Yash Patel demonstrated that the morphology of the cerebral cortex (the outer layer of the brain commonly called gray matter) differs depending on the psychiatric disorder, whether it is autism, schizophrenia or ADHD, for example.

The neurobiological factors at the origin of this modification during growth, on the other hand, remain for the most part to be identified.

The cerebral cortex, Professor Paus explained, hardly changes after the age of 2. It can therefore be studied in adulthood and have a very good idea of ​​its appearance before the manifestation of mental illness.

The researchers therefore performed a joint analysis compiling imaging data from 27,359 people. They were interested in the surface that the cerebral cortex would cover if it were unfolded on a flat surface. On average, that would be about 0.19 square meters (or two square feet), with a thickness of about 2.5 millimeters.

“We compared the surface between patients with different (mental health) problems and controls,” said Professor Paus. And the first thing we saw is that for some diseases there is a significant difference. But we also saw it in very young patients, say 10-year-old children, who had psychological problems, compared to children with very few psychological problems. »

But these differences were not uniform across the cerebral cortex, he added: They were more pronounced in regions of the cortex associated with more complex tasks like information processing, decision making and planning of future actions. They were therefore not regions associated with basic functions such as sight and hearing.

“Makes sense when you think about it, doesn’t it? asked Professor Paus. Psychiatric problems are not a matter of what one does not see or hear. It is complex thoughts or complex perceptions that are possibly disturbed. »

Early development

Professor Paus and his colleagues were then able to establish a link between the characteristics of these differences on the surface of the association cortex and those of the cellular events that underlie early brain development.

These differences, however, are only part of the puzzle, he said, and they offer no certainty that mental illness will manifest many years after birth. They also do not determine what mental illness, if any, will present.

“It’s just a matter of vulnerability,” said Professor Paus.

The researchers also discovered the point of convergence between these developmental processes and genes associated with perinatal risk factors, such as low birth weight, lack of oxygen supply, maternal hypertension and prematurity.

“The easiest thing to do would obviously be to manage these risk factors well,” Paus said.

But if this is not possible, he added, we could examine what we could do to cushion the impact of these adverse events during the first two years after birth, a period during which the development of the brain continues in fast motion. However, further research will be needed to verify this.

The findings of this study are published by the medical journal Biological psychiatry.

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