Depression, anxiety, schizophrenia, bipolar disorder, addiction and obsessive-compulsive disorder have all been linked to problems in the same circuit of brain regions
12 January 2023
The claim comes from an analysis of existing collections of medical data. The authors conclude that problems within the same brain network may be involved in depression, anxiety, schizophrenia, bipolar disorder, addiction and obsessive-compulsive disorder (OCD).
Brain-scanning studies have previously suggested that several different areas of the organ are linked with various mental health problems, but their results were inconsistent, says Joseph Taylor at Brigham and Women’s Hospital in Boston, Massachusetts. Taylor and his colleagues wondered if that inconsistency was because a number of different brain regions within one network could all play a role.
To learn more, the team looked at the health records of 194 Vietnam war veterans who had a physical injury to their brain. The veterans were more likely to be diagnosed with multiple mental health conditions, including the six previously mentioned, if they had damage to regions towards the back of the brain, including an area called the posterior parietal cortex, which is linked with spatial perceptions.
They were less likely to have such a diagnosis if they had been injured near the front of the brain, including in the anterior cingulate, a region associated with emotions, and the insula, which is linked with self-awareness.
The team compared its findings with an existing map of brain connections, known as a connectome. This revealed that when the identified regions at the back of the brain have low activity, the ones at the front tend to have high activity, and vice versa.
The researchers also looked at 193 brain-scanning studies involving nearly 16,000 people. They found that individuals with any of the six mental health conditions tended to have shrunken tissue in the regions at the front or in other areas linked to them.
Put together, the findings suggest that in people without any mental health condition, the back regions of the brain inhibit the front regions, while in people with damage to the back regions, the front regions become too active, which may lead to mental illness and tissue shrinkage, says Taylor.
This is supported by past surgeries carried out by other researchers that destroyed small parts of the brain in people with severe mental health conditions, such as OCD and depression that hadn’t responded to other treatments. All the sites that were destroyed were in the frontal regions.
Taylor’s team has dubbed the circuit the transdiagnostic network because it seems to be involved in so many different psychiatric diagnoses. He plans to boost brain activity in the posterior regions using a technique called transcranial magnetic stimulation as a potential treatment for mental illnesses.
The findings fit with the idea that rather than different mental illnesses having disparate causes, they may all have a shared underlying cause, or “p factor”. The idea is controversial because conditions such as depression and schizophrenia have very different symptoms.
“The results add to the growing weight of evidence that most psychiatric disorders share vulnerabilities,” says Terrie Moffitt at Duke University in Durham, North Carolina.
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