Exercise May Offset Genetic Risk for Depression

Regular exercise may help prevent depression in people who have a higher genetic risk for the disorder, according to a study posted November 5, 2019, in Depression & Anxiety. Moreover, patients do not have to run marathons to derive any benefit: Gentler forms of exercise such as walking and yoga also appear to offer some protection.

Although prior research has suggested that physical activity has positive effects on depression, this study answers two key questions in a more concrete way, said researcher Jordan W. Smoller, M.D. Sc.D., a professor of psychiatry at Harvard Medical School and a professor of epidemiology at Harvard T.H. Chan School of Public Health.

“Can we see a preventive effect of physical activity on new-onset depression in a real-world health care setting? And if so, do we see that effect even in people who may be genetically predisposed to develop depression?” asked Smoller, who is also the director of the Psychiatric and Neurodevelopmental Genetics Unit at Massachusetts General Hospital. “The answer to both questions is yes.”

To arrive at their conclusions, Smoller and colleagues analyzed data from 7,968 adults in the Partners Biobank, an ongoing study of patients in the Partners HealthCare hospital system in Massachusetts. The database contains patients’ electronic health records, genomic data, and data from lifestyle surveys to help researchers understand how genes, lifestyle, and environment affect health. Overall, roughly 8% of patients in the study were diagnosed with depression within two years of completing a baseline lifestyle survey that asked how much physical activity they engaged in each week.

First, the researchers divided the patients according to their polygenic risk score for depression.

“The polygenic risk score is a sum of the many small effects of genetic variations that may contribute to a trait, in this case, depression,” Smoller explained. The more variations people have, the greater their risk. Indeed, those with higher polygenic risk scores were significantly more likely to develop a new episode of depression over the two years.

Next, the researchers looked at the effect of physical activity. They found that the more physical activity patients reported, the less likely they were to develop depression. This effect was seen even in those with the highest polygenic risk for depression. For example, 12.7% of those in the high genetic risk group who exercised less than an hour a week developed depression, compared with 8.1% of those in the same group who exercised at least 3.2 hours a week, or an average of about 45 minutes a day. Both low-intensity exercise such as yoga and stretching and high-intensity exercise such as dancing, aerobics, and using exercise machines were associated with a lower risk of having a depressive episode, even after the researchers accounted for the patients’ polygenic risk score.

Combined with prior research to date, this study demonstrates that “there is now pretty compelling evidence that physical activity of many different kinds may reduce the risk of new-onset depression and symptoms of depression,” Smoller said.

He said he includes a discussion of exercise and physical activity in his visits with his patients and encourages other psychiatrists to do the same.

“[Psychiatrists] should be trained and educated to support physical activity as part of what we do in counseling our patients,” he said. Yet he acknowledged that the prospect of exercising may seem daunting to patients, so it is important to stress that they can start slowly.

This study was funded by the National Genome Research Institute and the National Institute of Mental Health. ■

“Physical Activity Offsets Genetic Risk for Incident Depression Assessed Via Electronic Health Records in a Biobank Cohort Study” is posted here.