The projected effect of increasing physical activity on reducing the prevalence of common mental disorders among Canadian men and women: a national population-based community study.

OBJECTIVE: Little quantitative research has been conducted on the effect of physical activity (PA) modification on the prevalence of mental disorders in a nationally representative sample. We aimed to provide quantitative evidence regarding the potential effectiveness of PA in the management of mental disorders.
METHODS: We used data from the national Canadian Community Health Survey of Mental Health and Well-being (CCHS 1.2) designed to represent the approximately the 25 million national community population aged 15 years and over in 2002.
RESULTS: Around 1 in 10 Canadians reported a 12-month mental disorder. Women reported more mood and anxiety disorders, men more substance dependence. Almost half of Canadians were physically inactive. After adjusting for covariates, physical inactivity was a significant risk factor for common mental disorders, except manic episode. Approximately 780,000 cases nationally are attributable to physical inactivity. A 10% reduction in the rate of physical inactivity would reduce common mental disorders by 167,000 cases, a 25% reduction would result in 389,000 fewer cases. PA was more beneficial for men.
CONCLUSIONS: Clinicians and public health campaigns targeting individual patients and general populations can improve patients' symptoms and prevent a significant proportion of future mental disorders by increasing the amount of PA.