title: Physical activity and the prevention of depression: a systematic review of prospective studies.
abstract: BACKGROUND
  Given its high prevalence and impact on quality of life, more research is needed in identifying factors that may prevent depression. This review examined whether physical activity (PA) is protective against the onset of depression.
  
  
  METHODS
  A comprehensive search was conducted up until December 2012 in the following databases: MEDLINE, Embase, PubMed, PsycINFO, SPORTDiscus, and Cochrane Database of Systematic Reviews. Data were analyzed between July 2012 and February 2013. Articles were chosen for the review if the study used a prospective-based, longitudinal design and examined relationships between PA and depression over at least two time intervals. A formal quality assessment for each study also was conducted independently by the two reviewers.
  
  
  RESULTS
  The initial search yielded a total of 6363 citations. After a thorough selection process, 30 studies were included for analyses. Among these, 25 studies demonstrated that baseline PA was negatively associated with a risk of subsequent depression. The majority of these studies were of high methodologic quality, providing consistent evidence that PA may prevent future depression. There is promising evidence that any level of PA, including low levels (e.g., walking <150 minutes/weeks), can prevent future depression.
  
  
  CONCLUSIONS
  From a population health perspective, promoting PA may serve as a valuable mental health promotion strategy in reducing the risk of developing depression.
authors.affiliation: Faculty of Kinesiology and Physical Education, Toronto, Ontario, Canada. Electronic address: george.mammen@mail.utoronto.ca.
authors.forename: George
authors.initials: G
authors.lastname: Mammen
authors.forename: Guy
authors.initials: G
authors.lastname: Faulkner
mesh_terms: D003863:Depression / Q000453:epidemiology / Q000517:prevention & control*; D015444:Exercise / Q000502:physiology; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D008603:Mental Health; D009043:Motor Activity / Q000502:physiology*; D015995:Prevalence; D011788:Quality of Life; D012107:Research Design; D016138:Walking / Q000502:physiology