Students who increase their physical activity during their middle-school years have fewer symptoms of depression, according to a new study.
Higher levels of physical activity at the start of the seventh grade were tied to lower levels of depression at the same point, while increased activity over the two years of the study was associated with reduced depressive symptoms at the end of the study, say Rod K. Dishman, Ph.D., of the University of Georgia and colleagues.
Their research appeared in the journal Psychosomatic Medicine.
“A naturally occurring change in physical activity across time was inversely associated with a change in levels of depressive symptoms across time,” Dishman says.
The practical magnitude of the change was small — affecting about 3 percent of the students — but statistically significant, he says, comparing it to the 8 percent effect found in a clinical trial of an SSRI, a common type of antidepressant medication.
The of 4,594 Minnesota students were asked if they got 20 minutes of exercise at least three times a week and took a standard test for adolescent depression. Other factors, like smoking, gender, alcohol use, socioeconomic status and attitudes about health, appearance and achievement were recorded too, but had no effect on the outcomes.
The children’s frequency of physical activity increased early in the study, but then leveled off. Dishman warned that stable levels of physical activity coupled with an increase in depression expected in early adolescence means parents and educators should take steps to keep children increasingly active.
Physical activity should be considered along with other preventive or treatment approaches to depression, like antidepressant drugs or psychotherapy, Dishman says. Furthermore, exercise has the benefit of being cheap and accessible and has few side effects.
“It is important to investigate the efficacy of low-risk interventions for reducing depression symptoms, such as physical activity, that may be more acceptable to youth and their families,” he says.