Does exercising really lighten your mood?

Exercise itself doesn't ease depression, according to a study that challenges the theory physical activity lightens patients' moods.

Twins who regularly exercised were no less likely to be depressed or anxious than their less-active siblings, according to the study of 5,952 twins from the Netherlands and 2,606 of their relatives. The study, published in the August issue of the Archives of General Psychiatry, suggested genetics may "best explain" why some people feel better after exercising.

Doctors have prescribed physical activity to improve mood based on studies that suggested "a casual effect of exercise on anxiety and depression," according to the study, conducted by the University of Amsterdam. The association "is not because of causal effects of exercise," the researchers wrote.

"Some genetic factors influencing exercise behavior may overlap with genetic factors influencing anxious and depressive symptoms," they wrote.

Exercise does help patients, said Susan Evans, director of the stress-reduction program at New York-Presbyterian Hospital in Manhattan. "Gold standard" research last year from Duke University linked exercise and mood, she said.

"The reality is that many of us who have been treating patients for years have prescribed exercise for mood and anxiety, and people who do it report feeling better," Evans said. The Duke study, lead by James A. Blumenthal, was the first and the best-designed study to measure the merits of exercise, according to Evans. That study suggested regular exercise works as well as antidepressant drugs. Blumenthal, in a telephone interview yesterday, said questions remained after his research.

"There still remain unresolved issues on whether giving people a prescription for exercise will lead to the same benefit as the research on volunteers that are receptive to exercise as a potential treatment," he said.