Exercise’s therapeutic potential for depression highlighted in new meta-analysis

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Various forms of exercise, including walking, jogging, yoga, and strength training, exhibit moderate effectiveness in alleviating symptoms of depression, according to new research published in The BMJ. This comprehensive analysis, which spans 218 studies involving over 14,000 participants, highlights the significance of exercise intensity in combating this pervasive mental health condition.

Depression, a major contributor to global disability, severely impacts life satisfaction and aggravates other health conditions. Despite the availability of drug treatments and psychotherapy, many individuals either do not respond to these interventions or face barriers to accessing them. This gap underscores the urgent need for additional evidence-based treatments.

Exercise, known for its wide-ranging benefits on physical and mental health, has been recognized as a potential therapeutic tool. However, existing guidelines offer varied recommendations on the type and amount of exercise, driving the need for a more definitive analysis.

“As a patient and psychologist, I rarely saw doctors prescribe exercise for depression,” said study author Michael Noetel, a senior lecturer of psychology at The University of Queensland. “Research showed exercise could help, but we didn’t know what to do. Was general encouragement good enough? If not, what should you prescribe? We wanted to look at all the evidence to find out what works best.”

The researchers conducted what is known as a network meta-analysis, a method that allows for the comparison of multiple treatment interventions simultaneously by evaluating direct comparisons within trials and indirect comparisons across trials. To be included in the analysis, studies needed to be randomized controlled trials focusing on exercise as a treatment for major depressive disorder.

The scope of the study was vast, drawing from 218 unique studies with a total of 495 arms and involving 14,170 participants, making it one of the largest analyses of its kind. The researchers extracted data on the type, frequency, intensity, and duration of the exercise interventions, alongside participant demographics such as age, sex, baseline severity of depressive symptoms, and any comorbidities.

The researchers found moderate reductions in depression symptoms attributable to several forms of physical activity. Walking or jogging, yoga, and strength training emerged as particularly effective, each showing moderate reductions in depressive symptoms when compared to active control conditions like usual care or placebo treatments.

The findings indicate that “exercise is a great treatment for depression,” Noetel told PsyPost.

Walking or jogging demonstrated the largest effect size, followed closely by yoga and strength training. Mixed aerobic exercises and practices such as tai chi or qigong also showed beneficial effects but to a slightly lesser degree.

A key finding of the study was the proportional relationship between the intensity of the exercise prescribed and the reduction in depression symptoms. This suggests that more vigorous activities could potentially offer greater benefits.

Jonathan Roiser, a professor of neuroscience and mental health at the University College London, who was not involved in the study, told the Science Media Centre: “The headline result is that all types of physical activity (especially aerobic exercise – which gets you sweaty and out of breath), cause a reduction in depressive symptoms; a similar conclusion to many reviews over the past decade.”

“The authors report a particularly large effect of dancing, but this should not be taken too seriously owing to the low number of studies included (5) each of which was quite small. Smaller effects (although still clinically important) were observed for milder types of activity, such as stretching or tai chi.”

“One striking finding was that the effect of aerobic exercise appeared to be numerically larger than for SSRIs, although there weren’t many head-to-head studies and so this result needs to be interpreted cautiously,” Roiser added.

Interestingly, the study also highlighted the acceptability of different exercise modalities, with strength training and yoga identified as the most tolerable forms of exercise. This aspect of the findings is particularly relevant for clinical practice, suggesting that these activities are not only effective but also likely to be embraced by individuals struggling with depression, thereby enhancing adherence to treatment programs.

The researchers also explored whether the benefits of exercise for depression varied according to certain demographic factors, such as the participants’ age and sex, but found that the effectiveness of exercise was broadly consistent across different groups.

“We were surprised exercise worked so well for so many people,” Noetel said. “The benefits were bigger than we expected. Exercise was as good as therapy and drugs. We were surprised that things like setting goals didn’t make exercise work better.”

“We thought giving more choices would help more but the more structure, the better people did. The support seems as important as the exercise itself. We were also surprised that the amount of exercise didn’t really matter; the intensity mattered more.”

Despite these promising results, the study’s authors caution that the overall confidence in the evidence is low to very low, primarily due to the high risk of bias within the included studies. Many studies lacked blinding of participants and personnel, a factor that could influence outcomes due to expectancy effects. This highlights the need for future research to address these limitations and further validate the efficacy of exercise as a treatment for depression.

“Some studies weren’t perfect,” Noetel noted. “People usually knew what the study was about (they weren’t often blinded). This makes the results a bit less certain. Double-blinded studies are stronger and the norm in medicine.”

“Some caution is needed in interpreting the findings,” added Paul Keedwell, a fellow of the Royal College of Psychiatrists. “Many studies had small sample sizes and were not conducted in real world conditions. Also, many depressed individuals find exercise very challenging.

“But, taken together, the evidence supports exercise being an important part of a package of treatments for depression, and it will help with physical health too. Depression is often associated with increased medical morbidity due to poor diet and inactivity.”

Regarding the long-term goals for this line of research, Noetel said: “We want to keep refining our understanding of how different types, intensities, and durations of exercise impact depression, and for whom they work best. Identifying the optimal exercise ‘dose’ and uncovering the mechanisms of action are key goals.”

“We also want to look at how to combine exercise with other treatments like therapy and medication to get the maximum benefit. Determining the best ways to support people in maintaining a long-term exercise habit to prevent relapse is another important avenue.”

“We want people to have more options for overcoming depression. Based on our findings, our big hope is that doctors will start prescribing exercise more regularly and with more structure.”

“Depression is a huge problem. Medication and therapy help but have limits,” Noetel added. “Many people can’t get them or don’t like the side effects. We think exercise is an important extra tool. It empowers people and improves physical health too. The next step is making exercise an easy treatment for everyone to access.”

The study, “Effect of exercise for depression: systematic review and network meta-analysis of randomised controlled trials,” was authored by Michael Noetel, Taren Sanders, Daniel Gallardo-Gómez, Paul Taylor, Borja del Pozo Cruz, Daniel van den Hoek, Jordan J Smith, John Mahoney, Jemima Spathis, Mark Moresi, Rebecca Pagano, Lisa Pagano, Roberta Vasconcellos, Hugh Arnott, Benjamin Varley, Philip Parker, Stuart Biddle, and Chris Lonsdale.

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