Physical activity and likelihood of depression in adults: a review.

OBJECTIVE: This review examines original research which has investigated associations between physical activity (PA) dose (i.e. frequency, intensity and duration) and domain and depression or symptoms of depression in adults.
METHODS: A search of electronic databases and authors' own bibliographic libraries was performed between 2006 and 2007 for original research articles investigating associations between PA and depression in adults. A total of 27 observational and 40 intervention studies were included.
RESULTS: Of the studies that focused on the association between duration of PA and likelihood of depression, all five observational studies, and five of the seven intervention studies found both shorter and longer durations of PA were associated with reduced likelihood of depression. Of the studies that focused on the association between intensity of PA and likelihood of depression, four of the six observational studies found that vigorous-intensity PA was more strongly associated with decreased likelihood of depression than lower intensities. Most intervention studies showed that both intensities were effective in reducing the likelihood of depression. Two observational studies found a stronger inverse relationship of leisure-time PA with depression than PA in other domains. There is insufficient evidence regarding the importance of the PA setting on depression.
CONCLUSION: Although the dose and domain of physical activity varied across studies reviewed, evidence suggests that even low doses of PA may be protective against depression. Further studies examining the optimal domain of PA for reducing the likelihood of depression are needed.