Dose-response relationship between physical activity and mental health: the Scottish Health Survey.

OBJECTIVES: Regular physical activity is thought to be associated with better mental health, although there is a lack of consensus regarding the optimal amount and type of activity to achieve these benefits. The association between mental health and physical activity behaviours was examined among a representative sample of men and women from the Scottish Health Surveys.
METHODS: Self-reported physical activity was measured and the General Health Questionnaire (GHQ-12) was administered in order to obtain information on current mental health. Participants were 19 842 men and women. Risk estimates per category of physical activity sessions per week were calculated using logistic regression models.
RESULTS: Psychological distress (based on a score of 4 or more on the GHQ-12) was evident in 3200 participants. Any form of daily physical activity was associated with a lower risk of psychological distress after adjustment for age, gender, social economic group, marital status, body mass index, long-standing illness, smoking and survey year (OR 0.59, 95% CI 0.52 to 0.66, p<0.001). A dose-response relationship was apparent, with moderate reductions in psychological distress with less frequent activity (OR 0.67, 95% CI 0.61 to 0.75). Different types of activities including domestic (housework and gardening), walking and sports were all independently associated with lower odds of psychological distress, although the strongest effects were observed for sports (OR 0.67, 95% CI 0.54 to 0.82).
CONCLUSION: Mental health benefits were observed at a minimal level of at least 20 min/week of any physical activity, although a dose-response pattern was demonstrated with greater risk reduction for activity at a higher volume and/or intensity.