Researchers have discovered a common pattern of gray matter loss in a spectrum of psychiatric disorders, ranging from schizophrenia to depression to addiction, according to a new meta-analysis of brain-imaging studies by Stanford University School of Medicine.
“The idea that these disorders share some common brain architecture and that some functions could be abnormal across so many of them is intriguing,” said Thomas Insel, M.D., director of the National Institute of Mental Health.
Previously, brain imaging studies tended to focus on one psychiatric disorder in isolation, whereas the Stanford researchers “have stepped back from the trees to look at the forest and see a pattern in that forest that wasn’t apparent when you just look at the trees,” Insel said.
The analysis of 193 peer-reviewed papers shows a loss of gray matter in three brain structures that, although physically separate, participate in a network associated with high-level functions, including planning and decision-making. The findings call into question the common practice of distinguishing psychiatric disorders by their symptoms rather than their underlying brain pathology.
“In many of these published studies we reviewed, researchers have tended to interpret their biological findings in terms of the one disorder they’re focusing on,” said Amit Etkin, M.D., Ph.D., an assistant professor of psychiatry and behavioral sciences at Stanford and the study’s senior author.
“We tried to ask a basic question that hasn’t been asked: Is there any common biological basis for mental illness?”
To find out, he and his research team gathered data from 193 separate studies containing, in all, magnetic-resonance images of the brains of 7,381 patients falling into six diagnostic categories: schizophrenia, bipolar disorder, major depression, addiction, obsessive-compulsive disorder and a cluster of related anxiety disorders.
They compared the images with those from 8,511 healthy control subjects, and identified three separate brain structures, several centimeters apart from one another, with a diminished volume of gray matter, the brain tissue that serves to process information. Gray matter loss in the three brain structures was similar across patients with different mental disorders, the researchers found.
These structures can be viewed as the alarm bell of the brain, Etkin said. “They work together, signaling to other brain regions when reality deviates from expectations — that something important and unpredicted has happened, or something important has failed to happen.”
Further analysis showed that gray-matter shrinkage in the three implicated brain structures was independent of any medication effects or overlapping psychiatric conditions.
In addition to the gray-matter loss in those three key areas, people with major depression also had gray-matter loss in other structures, including the hippocampus and amygdala, two important regions involved in storing memories and processing emotion, respectively.
Schizophrenia also featured reduced gray matter in several other structures, as well as an increase in gray matter in a region called the striatum, which Etkin suggested may be due more to the antipsychotic medications than the disease itself.
The findings are published in the journal JAMA Psychiatry.