By Marilyn Elias, USA TODAY | usatoday.com | March 17, 2008
BALTIMORE — The widely accepted view that exercise helps dispel depression and anxiety is misleading, since a common set of genes makes the most mentally healthy also the most prone to exercising, a scientist said over the weekend.
The controversial Dutch report on 7,200 twins and 1,200 of their siblings raises questions about large U.S. studies that show exercise improves mood even in those with major depression.
The Dutch study has followed participants for up to 11 years, says Eco DeGeus, a psychologist who specializes in exercise at Vrije University in Amsterdam. He spoke at the American Psychosomatic Society meeting here.
Using databases with twins and siblings lets scientists tease out genetic and environmental effects because identical twins share 100% of their genes; fraternal twins and siblings only share 50%. DeGeus’ study included questionnaires on exercise and evaluations of mental health every two years.
Changes in exercise didn’t correlate with improvements or declines in mental health, he says. Even if one identical twin began exercising he didn’t become less depressed or anxious than his twin.
Instead, says DeGeus, the evidence points to common genes influencing both mental health and exercise behavior: The most mentally healthy tend to be active, and genes, not environment, largely determine who they will be. “I’m not saying exercise might not help someone’s mood. But it also may not work at all,” he says.
Irrespective of genes, there’s strong evidence that exercise can improve symptoms of depression, says psychologist James Blumenthal of Duke University Medical Center. “I doubt that there’s no link between exercise and mood because again and again we’ve seen that when they become sedentary, people are more likely to get depressed, and becoming active improves mood,” says Blumenthal.
In another report at the meeting, there was an association between exercise and mental health in about 900 patients who came in to be evaluated for heart disease symptoms. Those who did no exercise had a 49% greater chance of being diagnosed with a psychiatric disorder, says health psychologist Simon Bacon of the Montreal Heart Institute. In fact, the more exercise someone got, the less his risk of having a mental health problem.
Genes probably help determine how much emotional payoff a person gets from exercise, says Bacon. “But if you can get someone who’s not exercising to become active, you’re probably going to see a benefit in their mental health,” he says.
When patients were evaluated for heart disease, those who said they did no exercise were more likely to be diagnosed with a mental disorder than those who did any exercise.
Percentage diagnosed with:
Any psychiatric disorder
Depression (mild to major)
Source: Simon Bacon, Montreal Heart Institute