In a review of several long-term studies published in the October 1999 issue of Reviews in the Neurosciences, Lupien concluded that this process is particularly damaging in the elderly. But there's no strong evidence that the hippocampus shrinks as a part of normal aging. In one recent study, Yvette Sheline, MD, a professor of psychiatry at Washington University in St. Louis, used magnetic resonance imaging to measure the hippocampus of 48 women aged 23 to 86, half of whom had a history of clinical depression, half of whom did not. The women with depression had smaller hippocampuses and scored lower on memory tests than the non-depressed group, regardless of age. We expected to see an effect from aging.
Research shows that when depression is treated, cognitive function, including memory, improves.
Still, more studies are needed to fully understand the connection between emotions and memory, cautions Mony de Leon, a psychiatrist and professor at New York University's medical school. The cortisol-hippocampus research is an exciting start, he says, but much remains a mystery. For example, researchers haven't yet determined what, if any, role cortisol plays in Alzheimer's disease. Studies show all people with Alzheimer's have hippocampal damage, but their cortisol production varies. It requires much more extensive investigation.