- One in five people have suffered or will suffer from depression in their life, 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 world health organization (WHO). These can be defined as a clinically severe impairment in an individual’s cognitive status, emotion regulation, or behavior. There are more.
Gray matter falls in certain brain areas
Researchers wanted to understand the areas 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 brain data from 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 emotion, and the insula, an area related to self-awareness. Inside, the gray matter was diminished. However, these areas of the brain are also affected by neurodegenerative diseases.
Mental illnesses: Damage to the transdiagnostic network increases 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 gray matter loss, common to all diagnoses of mental illness, that is the transdiagnostic network. It is therefore not the result of the decrease in gray matter that would be significant for mental illness, but rather the path that this change takes.
To narrow their research, the researchers analyzed the medical records of 194 Vietnam War veterans. They had a brain injury. The goal here was to see if the affected area had an impact on the mental disorder diagnosed in these veterans. And the results are compelling: indeed, those who had damage to the transdiagnostic network had a higher likelihood of suffering from multiple psychiatric disorders.
Psychiatric disorders and brain diseases: “more in common than we thought”
Nevertheless, according to the researchers, the reduction of the gray matter in the anterior cingulate and insula would not be the cause of the mental illness – contrary to what we previously thought – 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 of it’explains Joseph J. Taylor, one of the authors, in a communicated.
Researchers hope that identifying this transdiagnostic network specific to psychiatric illnesses will enable new studies and new advances in the understanding and management of mental disorders.
“Psychiatric disorders are brain disorders, and now we are 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 originally thought.”