THE ESSENTIAL
- One in five people has suffered or will suffer from depression in their lifetime, according to Inserm.
- Globally, schizophrenia affects approximately 0.7 to 1% of the population and 600,000 people in France.
In 2019, one in eight people worldwide – or 970 million people – had a mental disorder, according to the world health organization (WHO). These can be defined as a clinically major impairment in an individual’s cognitive status, emotion regulation, or behavior. There are several.
Gray matter decreases in certain brain areas
Researchers wanted to understand the regions of the brain involved in several of these mental disorders. They isolated six: depression, anxiety, schizophrenia, bipolar disorder, substance abuse and obsessive compulsive disorder (OCD).
To study them, they analyzed the brain data of 15,000 people. Among them, some did not suffer from mental illness and others did. Their results are published in the journal Nature Human Behavior.
In those who had mental disorders, certain areas of the brain were affected. These are the anterior cingulate, an area associated with emotions, and the insula, an area related to self-awareness. Inside, the gray matter was diminished. However, these regions of the brain are also affected by neurodegenerative diseases.
Mental illnesses: injuries on the transdiagnostic network increase the risk
To better understand how mental disorders specifically affect the brain, they analyzed the connectome, an existing map of human brain connections. Thus, they discovered a network specific to decreases in gray matter, common to all diagnoses of mental illness, it is the transdiagnostic network. It is therefore not the result of the decrease in gray matter that would matter for mental illnesses but rather the path taken by this alteration.
To narrow their research, the scientists analyzed the medical records of 194 Vietnam War veterans. They had a brain injury. The objective here was to see if the affected area had an impact on the mental disorder diagnosed in these veterans. And the results are convincing: indeed, those who had injuries on the transdiagnostic network had a higher probability of suffering from multiple psychiatric disorders.
Psychiatric and brain disorders: “more in common than we thought”
Nevertheless, according to the researchers, the reduction of the gray matter in the anterior cingulate and the insula would not be the cause of the mental illness – contrary to what we thought until now – but rather a consequence. “We found that damage to these regions—the anterior cingulate and insula—correlated with fewer psychiatric illnesses, so atrophy of this cingulate and insula may be a consequence or compensation for psychiatric illness rather than ‘a cause thereof’explains Joseph J. Taylor, one of the authors, in a communiqué.
Scientists hope that the identification of this transdiagnostic network specific to psychiatric diseases will allow new studies and new advances in the understanding and management of mental disorders.
“Psychiatric disorders are brain disorders, and now we’re just beginning to have the tools to study and modulate their underlying circuitry.concludes Joseph J. Taylor. There may be more commonalities between these disorders than we initially thought.”
