Depressed Adolescents Have Altered Brain Structure

Study finds hippocampus is smaller

THURSDAY, Jan. 29, 2004 (HealthDayNews) -- The area of the brain called the hippocampus is smaller in adolescents with major depression compared to their healthy peers, researchers report.

Major depressive disorder is a severe, common and debilitating illness with alarming rates of medical problems and death. And there is evidence that child and adolescent depression leads to adult depression, says a report in the Jan. 29 issue of BMC Medicine.

"We are finding biological factors that seem to be involved with major depression," says study author Frank MacMaster, a Ph.D. candidate in the department of anatomy and neurobiology at Dalhousie University in Halifax, Nova Scotia. "A lot of people have stigmatized depression, but it is a real medical condition."

The hippocampus is associated with motivation, emotional control and memory, and plays a role in controlling the body's response to stress, MacMaster says.

Results of studies that measured the size of the hippocampus in adults with depression have disagreed about whether there is a difference in hippocampal size between healthy and depressed adults.

In this first study to measure hippocampal size in teens, researchers studied 34 adolescents aged 13 to 18. Seventeen of the patients had major depressive disorder, while the others didn't.

All the teens had a magnetic resonance imaging (MRI) scan, and the researchers measured the volume of their left and right hippocampus.

The investigators found the hippocampus of teens with major depressive disorder was, on average, 17 percent smaller than the non-depressed teens. This size difference was particularly prominent in the left hippocampus, they report.

"I was surprised by the amount of difference in hippocampal size, which is on the high side of the hippocampal size difference seen between depressed and healthy adults," MacMaster says.

MacMaster believes these results indicate there is a genetic component to major depression, which probably involves several genes. "But we have not found the smoking gun gene yet," he says.

With drugs and other interventions, the prognosis of depression in teens is hopeful, MacMaster says. "Becoming aware of a child's depression is the real front line from a clinical point of view," he adds.

The goal of this research is to identify biomarkers that will aid doctors in diagnosing adolescent depression, he says.

MacMaster stresses that depression in adolescents "is a biological, medical condition. It's not a character flaw arising from poor parenting."

Dr. Joseph L. Price, a professor of anatomy and neurobiology at Washington University in St. Louis, says other studies have found differences in hippocampal volume in older patients with major depression.

And some studies have found that women with major depression had a smaller corpus callosum, which connects the left and right halves of the brain. The same thing was found in the children of these women, indicating that they, too, have an increased risk for depression, Price says.

Price adds that, in his own work, he has found changes in some types of brain cells in people with major depression compared to healthy patients.

Taken together, all these studies "indicate that there are several physical changes in the brain that underlie major depression," Price says. "All this might not help us treat the disease, but it will help us understand it."

Dr. Hillary Blumberg, an assistant professor of psychiatry at Yale University, adds this study is important because it may lead to identifying a biological marker that can diagnose depression in teens.

"This is a very hopeful message, because it suggests that we are developing a better sense of where to look in the brain to understand the development of depression." And this may lead to better treatment, she says.

More information

For more on adolescent depression, check out the National Mental Health Association or the National Institute on Mental Health.

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