Prospective associations between physical activity and clinician diagnosed major depressive disorder in adults: A 13-year cohort study.

Regular physical activity (PA) appears to protect against the emergence of depression, but prospective studies linked to clinician diagnoses of major depressive disorder (MDD) remain scarce. It is also unclear whether PA levels recommended for general health are prospectively related to depression onset. We explored these relationships in a cohort of adults followed over 13 years. In total, 43,863 Swedish adults were surveyed in 1997 and responses linked to clinician-diagnosed MDD obtained from specialist medical registers until 2010. Weekly durations of habitual moderate (including walking) and vigorous PA were self-reported. Relationships between total durations of PA, 0-149 ('below'), 150-299 ('achieve'), and ≥300 min ('exceed') with incident MDD were explored using survival analysis with Cox proportional hazards regression. Models were adjusted for relevant covariates. Those with indications of depression at baseline were removed from the primary analyses. Of 25,520 participants with complete data (mean age = 49 years, SD = 16, 65% female), 76% met the recommended weekly duration of PA (≥150 min), and 38% exceeded this duration (≥300 min). During 13-years follow-up 549 MDD cases (1.5%) were identified (incidence rate = 111 cases per 100,000 person-years). Compared to participants who were below, those who exceeded the recommended weekly duration (≥300 min/week) had 29% reduced risk of depression onset (HR 0.71, 95% CI = 0.53-0.96). A non-significant inverse association was observed among those who achieved the minimum duration of 150-min/week (HR 0.86, 95% CI = 0.64-1.14). Habitual PA levels that exceed the duration recommended for general health may reduce the risk of clinician-diagnosed major depression in adults.