Psychiatric disorders, traditionally distinguished from one another based on symptoms, may in reality not be as discrete as we think.
In a huge meta-analysis just published in JAMA Psychiatry, Stanford neuroscientist and psychiatrist Amit Etkin, MD, PhD, and his colleagues pooled the results from 193 different studies. This allowed them to compare brain images from 7,381 patients diagnosed with any of six conditions - schizophrenia, bipolar disorder, major depression, addiction, obsessive-compulsive disorder, and a cluster of anxiety syndromes - to one another, as well as to brain images from 8,511 healthy patients.
Compared with healthy brains, patients in all six psychiatric categories showed a loss of gray matter in each of three separate brain structures. These three areas, along with others, tend to fire in synchrony and are known to participate in the brain's so-called "executive-function network," which is associated with high-level functions including planning, decision-making, task-switching, concentrating in the face of distractions, and damping counterproductive impulses.
The findings call into question a longstanding tendency to distinguish psychiatric disorders chiefly by their symptoms
("Gray matter" refers to information-processing nerve-cell concentrations in the brain, as opposed to the "white matter" tracts that, like connecting cables, shuttle information from one part of the brain to another.)
As Etkin told me when I interviewed him for the news release we issued on this study, "these three structures can be viewed as the alarm system for the brain." More from our release:
"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." That signaling guides future behavior in directions more likely to obtain desired results.
The studies of psychiatric patients that Etkin's team employed all used a technique that yields high-resolution images of the brain's component structures but can say nothing about how or when these structures work or interact with one another. However, that kind of imaging data was available for the healthy subjects. And, on analysis, those healthy peoples' performance on classic tests of executive-function (such as asking the test-taker to note the color of the word "blue," displayed in a color other than blue, after seeing it briefly flashed on a screen) correlated strongly with the volume of gray matter in the three suspect brain areas, supporting the idea that the anatomical loss in psychiatric patients was physiologically meaningful.
The findings call into question a longstanding tendency to distinguish psychiatric disorders chiefly by their symptoms rather than their underlying brain pathology - and, by implication, suggest that disparate conditions may be amenable to some common remedy.
As National Institute of Mental Health Director Thomas Insel, MD, told me in an interview about the study, the Stanford investigators "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."
Previously: Hope for the globby thing inside our skulls, Brain study offers intriguing clues toward new therapies for psychiatric disorders and Study shows abnormalities in brains of anxiety-disorder patients
Photo by Philippe Put