Data Indicate Physical Activity Lowers Depression Risk
A novel study that used Mendelian randomization to gauge whether physical activity reduces the risk of depression or depression leads to reduced physical activity has generated evidence for the former. Physical activity seems to protect against depression, researchers reported in JAMA Psychiatry online.
“Using genetic data, we found evidence that higher levels of physical activity may causally reduce risk for depression,” said lead author Karmel Choi, PhD, of the Psychiatric and Neurodevelopmental Genetics Unit in the Massachusetts General Hospital Center for Genomic Medicine, Boston. “Knowing whether an associated factor actually causes an outcome is important, because we want to invest in preventive strategies that really work.”
The study used gene variants from the results of genome-wide association studies for physical activity and for depression. Results for physical activity were available for 377,000 people’s self-reports of physical activity and 91,000 people’s readings of motion-detecting sensors called accelerometers. Results for depression were available for more than 143,000 people with and without major depressive disorder.
Accelerometer-based physical activity, but not self-reported physical activity, appeared to protect against depression, researchers reported. The difference, they explained, could be due to inaccuracies in memories or a desire to appear in a more positive light in subjective self-reports. Objective accelerometer-measured activity, meanwhile, measures not only planned physical activity but also unplanned tasks, such as taking the stairs or mowing the lawn, that self-reports may fail to account for.
Researchers found no evidence that depression reduced either accelerometer-based or self-reported physical activity.
“On average,” said Dr. Choi, “doing more physical activity appears to protect against developing depression. Any activity appears to be better than none. Our rough calculations suggest that replacing sitting with 15 minutes of a heart-pumping activity like running, or with an hour of moderately vigorous activity, is enough to produce the average increase in accelerometer data that was linked to a lower depression risk.”
Choi KW, Chen CY, Stein MB, et al. Assessment of bidirectional relationships between physical activity and depression among adults: a 2-sample mendelian randomization study. JAMA Psychiatry. 2019 January 23;[Epub ahead of print].