(RxWiki News) Exercise has been shown to have a positive effect on symptoms of depression. But these mental health benefits may not be the same in young people as in others.
A study in the UK looked at whether exercise could prevent later depression in adolescents.
The study authors found that the children's physical activity in their early teen years did not appear to affect whether they were depressed a few years later.
“Our findings do not eliminate the possibility that [physical activity] positively affects depressed mood in the general population; rather, we suggest that this effect may be small or nonexistent during the period of adolescence,” the authors wrote.
"Sometimes science disappoints," said Glen Elliott, PhD, MD, a clinical professor at the Stanford University Department of Psychiatry and Behavioral Sciences. "Appealing as the idea may be that physically active individuals are in some way protected against certain risks, including depression, there is no strong theoretical basis for such a belief.
"These investigators found that at least baseline levels of physical activity had no effect, good or bad, on risk of depression three years later," said Dr. Elliott, who was not involved in this study.
"As they point out, that is not to suggest that physical activity has no other benefits, nor does it address a separate question of whether increased physical activity might have be beneficial for someone who is depressed," he said.
For this study, Umar Toseeb, PhD, from the University of Cambridge in the UK, and colleagues studied 736 children who were 14.5 years old on average.
According to the National Institute of Mental Health, almost 11 percent of young people are depressed by age 18. There has been little research on whether exercise can affect depression in this age group.
Dr. Toseeb and team measured the amount of exercise the children did each day. The youth in the study wore a monitor that recorded their heart rate and sensed their movements.
The team measured which activities were moderate and vigorous physical activities (MVPAs). They defined MVPAs as activities that were four or more times as strenuous as sitting — measured by heart rate and movements.
Three years later, the research team looked at mood and depression symptoms in the kids.
The study authors found that the amount of exercise children got when they were around 14 years old did not predict whether they would be depressed at age 17. Children who were active at early ages did not have an increased or decreased risk for depression a few years later.
The results were the same in boys and girls.
The authors noted that their study did not assess the effects of short-term activity — activity done closer to age 17 — on depression.
The study was published online Oct. 14 in JAMA Pediatrics.
Grants from the Wellcome Trust and the Medical Research Council funded the research. The authors declared no conflicts of interest.