What is the dose-response association between physical activity and incident depression in adults?

Pearce M, Garcia L, Abbas A, et al. (2022). Association Between Physical Activity and Risk of Depression: A Systematic Review and Meta-analysis. JAMA Psychiatry, 79(6), 550–559.

Our results show an inverse curvilinear association with the greatest differences in risk observed between low doses of physical activity, suggesting most benefits are realized when moving from no activity to at least some.

Activity - Accumulating an activity volume equivalent to 2.5 hours of brisk walking per week was associated with 25% lower risk of depression, and at half that dose, risk was 18% lower compared with no activity. Only minor additional benefits were observed at higher activity levels.

Small volumes of activity - We also found that even small volumes of activity were beneficial but go further by quantifying differences in risk for these doses. Our findings therefore have important new implications for health practitioners making lifestyle recommendations, especially to inactive individuals who may perceive the current recommended target as unrealistic.

Brain answers - The associations we observed are likely explained by more than 1 mechanism. Proposed pathways include acute neuroendocrine and inflammatory responses to activity such as activation of the endocannabinoid system (“runner’s high”) and longer-term adaptations, including changes in the brain’s neural architecture.

Social dimensions - Psychosocial and behavioral explanations have also been suggested, including improved physical self-perceptions and body image, more social interactions, and the personal development of coping strategies. The social aspect of activity participation may operate even at relatively low doses, consistent with the dose-response curve we observed.

Green space - The use of green space is associated with lower risk of depression, with mediation analysis suggesting only part of the association is explained by physical activity. Conversely, noise pollution⁴⁹ and neighborhood deprivation⁵⁰ might diminish the mental health benefits of activity.