Can Exercise Truly Combat Depression? A Look at the Evidence

Many previous studies have found exercise to be both preventative and a powerful treatment for existing depression. In one recent study, researchers found that one out of every two people who exercise will experience improvement—far better than the seven or more who require antidepressant drug treatment before a single person benefits. And another meta-analysis found that exercise, including walking and jogging, beat both cognitive behavioral therapy and antidepressants for treating even severe depression. For this reason, researchers have written that exercise meets the criteria to be considered an “evidence-based treatment for depression.” Yet the psychiatric establishment continues to relegate exercise to an “add-on” for those who are already interested in it—instead clinging to the treatment paradigm that focuses on antidepressant drugs and therapy. Now, a new Cochrane meta-analysis—reviewing the existing randomized, controlled studies on exercise for depression—has concluded that exercise is just as good as therapy or antidepressants at treating depression. Exercise beat placebo with a moderate-to-large effect size. Cochrane is an international nonprofit whose systematic reviews are widely considered the gold standard for rigorous scientific research. The authors were based at the University of Lancashire, UK. “Our findings suggest that exercise appears to be a safe and accessible option for helping to manage symptoms of depression,” lead author Andrew Clegg said in an accompanying statement. The new study updates the 2008 and 2013 Cochrane publications on the subject, and the new evidence doesn’t change their earlier results: exercise looks good, holding its own compared with therapy and antidepressants. However, the current version adds to the totality of evidence, with 35 new trials of exercise added to the Cochrane analysis. In total, the researchers included 73 trials of exercise for depression, totaling about 5,000 participants. Sixty-nine trials were able to be statistically analyzed. The efficacy of exercise was calculated as standardized mean difference (SMD). The SMD for exercise over placebo was −0.67, which they class as a moderate-to-large effect. The evidence that exercise is as good as therapy received a “moderate certainty” rating from the researchers, based on 10 trials that compared the two approaches. There was no difference between exercise and therapy outcomes, even at long-term follow-up. The evidence that exercise is as good as antidepressants received a “low certainty” rating because it was based on fewer trials (five), only one of which included long-term outcomes. However, in those trials, there was no difference between exercise and antidepressant outcomes. One of the main critiques of exercise is that people won’t do it—that taking drugs or even going to therapy is an easier sell than exercise. Yet this review found that exercise was just as acceptable as drugs or therapy, with about the same number of participants completing treatment in each group. And exercise has much lower potential for harm—and many other benefits—compared with antidepressant drugs. (For instance, one recent study found that running was just as good as antidepressants, and that those who engaged in running ended up improving their physical health too—while those who took antidepressants had worsening physical health over time.) “Exercise is low-cost, widely available, and comes with additional health benefits, making it an attractive option for patients and healthcare providers,” according to the accompanying statement. The researchers found that light to moderate intensity exercise may have been slightly more beneficial than vigorous exercise. They also found that the “sweet spot” for number of exercise sessions appeared to be between 13 and 36. In psychiatric science, one of the biggest issues is replication—can additional studies show that this positive effect is consistently true? In this case, the updated Cochrane review demonstrates that exercise’s efficacy for depression treatment is not a fluke. The additional trials since the last review serve to add consistent evidence showing the efficacy of exercise for depression. Because participants know whether they engaged in exercise or not, they could not be blinded to outcomes. Thus, Cochrane’s editors instructed the authors to rate all the trials as having “high risk of bias” due to unblinding. But, the authors write, “in exercise trials, participants cannot be blinded to the treatment allocation.” The limited number of trials comparing exercise to therapy and antidepressants, and the fact that these were small, short-term studies, are the biggest limitations to being able to implement these findings. Although we have consistent evidence that exercise is effective, and studies continue to find it to be at least as good as therapy and drugs for depression, there remain questions about long-term results and how trustworthy the findings are. Because of this, Clegg calls for higher quality studies that can overcome these limitations. “Exercise can help people with depression, but if we want to find which types work best, for who and whether the benefits last over time, we still need larger, high-quality studies. One large, well-conducted trial is much better than numerous poor quality small trials with limited numbers of participants in each,” Clegg said in the accompanying statement. ****