Study links cortex to depression

Scientists who have been following families with a history of depression have found structural differences in family members' brains — specifically, a significant thinning of the right cortex, the brain's outermost surface. The thinning may be a trait or a marker of vulnerability to depression, the researchers suggested.

The scientists' brain-imaging study found the thinning in descendants of depressed parents and grandparents, whether or not the individuals themselves had ever suffered a depressive episode or an anxiety disorder, researchers said.

"That's what is so extraordinary. You're seeing it two generations later, and you're seeing it in both children and adults," said Dr. Bradley Peterson, a professor of psychiatry at Columbia College of Physicians and Surgeons and the paper's first author. "And it's present even if those offspring themselves have not yet become ill."

While people may assume that a familial trait is genetic, that is not necessarily the case, Peterson added. "We don't know if this has a genetic origin or if it's a consequence of growing up with parents or grandparents who are ill. Studies have shown that when parents are depressed, it changes the environment in which children are growing up."

The paper, to be published in the Proceedings of the National Academy of Sciences, is an outgrowth of research started 27 years ago by Dr. Myrna Weissman, senior author of the paper, to investigate the familial roots of depression.

The scientists conducted brain imaging of 131 individuals, including children and adults ages 6 to 54, about half of whom were considered at high risk for depression because of their family history and half of whom were in a low-risk group.

Maps of cortical thickness showed significant thinning of 28 percent on average across broad expanses of the right cerebral hemisphere in the high-risk group, compared with the low-risk group, the paper reported.

The cerebral cortex is the region of the brain centrally involved in reasoning, planning and mood, and thinning of the cortex may affect an individual's ability to pay attention to and interpret social and emotional cues, scientists suggested.