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Hippocampus shrinks in patients with recurrent depression

Researchers are not clear whether the shrinkage is caused by depression or is a risk factor for it.

By Stephen Feller

SYDNEY, June 30 (UPI) -- A new study has found that people with major depressive disorder, recurring bouts of depression over the course of one's lifetime, have a smaller hippocampus than people who do not have the disorder.

Researchers said they are unclear whether the difference in the size of the hippocampus, the part of the brain most associated with forming new memories, was a result of chronic stress because of depression or a risk factor for depression.

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"This large study confirms the need to treat first episodes of depression effectively, particularly in teenagers and young adults, to prevent the brain changes that accompany recurrent depression," said Ian Hickie, a professor at the University of Sydney and director of its Brain and Mind Research Institute, in a press release.

Major depression, which affects 1 out of 6 people at some point in their lives, is characterized by feelings of sadness, frustration, loss, or anger that interfere with a person's everyday life for weeks, months or years at a time.

The study, the largest international study to compare brain sizes for this purpose, had researchers analyzing neuroimaging data from 1,728 major depressive disorder patients and 7,199 healthy people.

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Patients who had experienced only their first episode of major depression did not show the difference in hippocampal sizes, which leads researchers to consider that recurring depressive stress may play a role in causing the shrinkage.

"This new finding of smaller hippocampal volume in people with major depression may offer some support to the neurotrophic hypothesis of depression," said Jim Lagopoulos, an associate professor at the institute. "Clearly, there's a need for longitudinal studies that can track changes in hippocampal volume among people with depression over time, to better clarify whether hippocampal abnormalities result from prolonged duration of chronic stress, or represent a vulnerability factor for depression, or both."

The study is published in Molecular Psychiatry.

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