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 S. 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, Dr. 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.”