MD, PhD, MAE, FMedSci, FRSB, FRCP, FRCPEd.

The aim of this systematic review and network meta-analysis was to identify the optimal dose and modality of exercise for treating major depressive disorder, compared with psychotherapy, antidepressants, and control conditions.

The screening, data extraction, coding, and risk of bias assessment were performed independently and in duplicate. Bayesian arm based, multilevel network meta-analyses were performed for the primary analyses. Quality of the evidence for each arm was graded using the confidence in network meta-analysis (CINeMA) online tool. All randomised trials with exercise arms for participants meeting clinical cut-offs for major depression were included.

A total of 218 unique studies with a total of 495 arms and 14 170 participants were included. Compared with active controls (eg, usual care, placebo tablet), moderate reductions in depression were found for

  • walking or jogging,
  • strength training,
  • mixed aerobic exercises,
  • and tai chi or qigong.

The effects of exercise were proportional to the intensity prescribed. Strength training and yoga appeared to be the most acceptable modalities. Results appeared robust to publication bias, but only one study met the Cochrane criteria for low risk of bias. As a result, confidence in accordance with CINeMA was low for walking or jogging and very low for other treatments.

The authors concluded that exercise is an effective treatment for depression, with walking or jogging, yoga, and strength training more effective than other exercises, particularly when intense. Yoga and strength training were well tolerated compared with other treatments. Exercise appeared equally effective for people with and without comorbidities and with different baseline levels of depression. To mitigate expectancy effects, future studies could aim to blind participants and staff. These forms of exercise could be considered alongside psychotherapy and antidepressants as core treatments for depression.

As far as I can see, there are two main problems with these findings:

  1. Because too many of the studies are less than rigorous, the results are not quite as certain as the conclusions would seem to imply.
  2. Patients suffering from a major depressive disorder are often unable (too fatigued, demotivated, etc.) to do and/or keep up vigorous excerise over any length of time.

What I find furthermore puzzling is that, on the one hand, the results show that – as one might expect – the effects are proportional to the intensity of the excercise but, on the other hand tai chi and qugong which are both distinctly low-intensity turn out to be effective.

Nonetheless, this excellent paper is undoubtedly good news and offers hope for patients who are in desperate need of effective, safe and economical treatments.

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