Lost in the darkness

2019-03-08 04:18:01

By Jonathan Knight DEPRESSION may cause permanent brain damage, a new report suggests. Brain scans have revealed that a region involved in memory is slightly smaller in women who suffer frequent bouts of depression. Certain hormones found at high levels in clinically depressed people are known to kill neurons in animals. But so far attempts to measure the effects of depression on the human brain have been inconclusive. To find out more, Yvette Sheline and her colleagues at Washington University in St Louis, Missouri, used magnetic resonance imaging to scan the brains of 24 women with a history of depression. None of the women had suffered a bout for at least four months. In each case, the researchers also scanned the brain of a healthy person of matching age and educational level. From the scans, Sheline worked out the volume of the hippocampus, a structure at the base of the brain that is essential for the formation of new memories. She reports in The Journal of Neuroscience(vol 19, p 5034) that in the depressed women the hippocampus was on average 10 per cent smaller than in the controls. Furthermore, the number of episodes of depression a patient had suffered correlated with the amount of hippocampal shrinkage. So Sheline believes the depression caused the damage and not the other way around. “It’s highly significant,” she says. “I don’t have any doubt that there is a real effect.” Most of the women had used antidepressant drugs, but other experiments have found no harmful effects of such drugs on brain cells. Stress hormones released during depression may cause the shrinkage, which appears to affect memory. On average, the depressed women had slightly more trouble memorising lists of words than the controls. They also scored less well on a test involving spatial memory. Sheline says previous brain scan studies missed the effect because they did not record small detail: one had a resolution of 5 millimetres,