Fifteen minutes of vigorous activity or approximately 1 hour of moderate activity (like walking or gardening)—or a combination of light and vigorous physical activity—may significantly reduce risk of major depression, according to a study published in JAMA Psychiatry (2019; doi:10.1001/jamapsychiatry.2018.4175).
Researchers from Harvard University and members of the Major Depressive Disorder Working Group of the Psychiatric Genomics Consortium conducted the study using mendelian randomization, a form of analysis that relies on genetic evidence. Genome data came from large-scale genome-wide association studies with a combined sample size of 611,583 male and female adults.
“Using genetic data, we found evidence that higher levels of physical activity may causally reduce risk for depression,” said lead study author Karmel Choi, PhD, of the Psychiatric and Neurodevelopmental Genetics Unit in the Massachusetts General Hospital Center for Genomic Medicine. “Knowing whether an associated factor actually causes an outcome is important, because we want to invest in preventive strategies that really work.”
Choi added, “And of course it’s one thing to know that physical activity could be beneficial for preventing depression; it’s another to actually get people to be physically active. More work needs to be done to figure out how best to tailor recommendations to different kinds of people with different risk profiles. We are currently looking at whether and how much physical activity can benefit different at-risk groups, such as people who are genetically vulnerable to depression or those going through stressful situations, and [we] hope to develop a better understanding of physical activity to promote resilience to depression.”
Principal investigator Jordan Smoller, MD, ScD, director of the Psychiatric and Neurodevelopmental Genetics Unit and professor of psychiatry at Harvard Medical School, said, “These very large studies can help us look at a question such as whether physical activity—or the tendency to engage in more physical activity—has a likely causal effect on depression. And the answers to those questions could help researchers design large-scale clinical trials.”