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Depressive disorders are the second leading cause of global burden of illness and account for more than 44 million years lived with disability, according to Felipe B. Schuch, Ph.D., of LaSalle University in Canoas, Brazil, and colleagues.
While previous reviews have suggested that physical activity can protect against the development of depression, this study is believed to be “the first pooled meta-analysis investigating this relationship, which allows a clearer understanding of a true association between an exposure and outcome, rather than when studies are considered separately,” Schuch and colleagues wrote.
The meta-analysis included 49 studies involving nearly 267,000 participants from across four geographic regions (Asia, Europe, North America, and Oceania), who were followed for an average of 7.4 years. Participants were free of depression or depressive symptoms at the outset of the studies.
The study found overall that people with higher levels of physical activity were significantly less likely to develop depression, compared with people with low levels of physical activity (adjusted odds ratio=0.83). Physical activity had a protective effect against the emergence of depression in young people (adjusted odds ratio=0.90), adults (adjusted odds ratio=0.78), and in elderly people (adjusted odds ratio=0.79). Protective effects against depression were found across geographical regions, with adjusted odds ratios ranging from 0.65 to 0.84 in Asia, Europe, North America, and Oceania, and against major depression diagnosis (adjusted odds ratio=0.86).
“Our meta-analysis suggests that physical activity is associated with a decrease in the risk of developing depression, which raises an inevitable question: How might physical activity offer protection against depression onset?” the authors wrote. “It is likely that no single mechanism can explain this relationship. A range of biochemical and psychosocial factors are likely responsible, including biological mechanisms through which exercise increases neurogenesis and reduces inflammatory and oxidant markers and activates the endocannabinoid system.”
“Our data further emphasize the importance of policies targeting increased physical activity levels,” they concluded. However, randomized, controlled trials are needed to discern whether physical activity can prevent the development of depression in those at highest risk of the disorder.
For related information, see the Psychiatric News article “Minimal Exercise May Help Prevent Future Depression.”
(Image: iStock/kali9)
