A brain imaging study of several generations of participating families found structural differences in those with a history of depression.
Thinning in the cerebral cortex, which is the outermost surface of the brain, indicates a vulnerability to depression. Brain scans showed a 28-percent thinning in the right cerebral cortex in people who had a family history of depression compared with people who did not. The cerebral cortex controls reasoning, planning and mood; and thinning of the cerebral cortex may increase the risk of depression by disrupting a person’s ability to decode and remember social and emotional cues from other people.
“If you have thinning in this portion of the brain, it interferes with the processing of emotional stimuli, ” said Dr. Bradley S. Peterson, a professor of psychiatry at Columbia College of Physicians and Surgeons and the paper’s first author. “We think that’s what makes them vulnerable to developing anxiety and depression - it essentially isolates them in an emotional world.”
The thinning existed in descendants of depressed parents and grandparents, whether or not those individuals had ever experienced depression or anxiety.
“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. Peterson. “And it’s present even if those offspring themselves have not yet become ill.”
“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…” grow up.
“Because previous biological studies only focused on a relatively small number of individuals who already suffered from depression, their findings were unable to tease out whether those differences represented the causes of depressive illness, or a consequence, ” Peterson said.
Peterson and his team conducted memory and attention tests on the study subjects and found that those with more thinning in the right cortex performed worse on attention and memory tests.
“Our findings suggest rather strongly that if you have thinning in the right hemisphere of the brain, you may be predisposed to depression and may also have some cognitive and inattention issues,” he said.
The findings suggest that, in addition to antidepressants, other medications (such as stimulants) might prove helpful in treating depression in some patients.
The findings will be published in Proceedings of the National Academy of Sciences, and is based on research started 27 years ago by Dr. Myrna Weissman to investigate the familial roots of depression. Weissman and her colleagues conducted brain imaging on 131 people between the ages of 6 and 54. Half of the participants were at high risk for depression because of family history. Half were low-risk.
Doctors Weissman and Peterson add to an arsenal of information that enables us to better understand the root causes of depression. From this understanding better diagnosis and treatment will grow.