Exercise cut depression symptoms sharply in young people, but the evidence is shaky

Depression often first appears in adolescence and young adulthood, and not every young person responds to, or wants, talking therapy or medication. Physical activity is cheap, familiar and free of drug side effects, which makes it an attractive candidate as an actual treatment rather than just a feel-good extra. Most of the research on exercise and depression has been done in adults, so the question of whether it works for people aged 12 to 25 with a diagnosis or clear symptoms has lacked a firm answer. This review set out to pool every randomised trial in that age group and put a number on the effect.

The authors searched four databases up to September 2016 for randomised controlled trials of physical activity interventions in adolescents and young adults aged 12 to 25 who had a diagnosis of depression or symptoms above a clinical threshold. Seventeen trials were eligible and 16 provided usable data from 771 participants. Results were pooled using a random-effects model, with subgroup analyses and meta-regression to look for factors that changed the effect. Acceptability was judged by dropout rates, each trial was assessed for risk of bias, and the overall quality of evidence was graded using GRADE criteria.

Physical activity produced a large improvement in depression symptoms compared with control conditions, with a standardised mean difference of -0.82. The effect held up in the five trials that recruited clinical samples and in the seven trials that used attention or activity placebo controls, which strengthens the case that the exercise itself mattered. Dropout was 11% in the physical activity arms and essentially the same as in controls, suggesting young people found it acceptable. However, the quality of the evidence was downgraded two levels to low, because of risk of bias in the trials and suspected publication bias.

This review supports physical activity as a promising and acceptable intervention for depression in young people, extending a literature that has mostly focused on adults. At the same time, the low quality grading means the size of the effect should be read cautiously, and the authors call for robust clinical effectiveness trials that minimise bias. Exactly what kind of exercise works best remains unclear, though the best candidates on current evidence are supervised, aerobic-based activity at moderate-to-vigorous intensity, done multiple times per week for eight or more weeks. Whether the benefit persists after a programme ends is another open question.

If you are a young adult dealing with low mood, or you care about one, this is a reason to take movement seriously as part of the picture rather than dismissing it as a platitude. The pooled effect was large, and young people in these trials did not abandon the programmes any faster than the alternatives, which addresses the common worry that depressed people simply will not exercise. It is not evidence that exercise replaces professional care, and the low quality grading means the true benefit could be smaller than it appears. The pattern that looked most promising was structured, supervised aerobic activity sustained over a couple of months rather than one-off efforts.