title: Longitudinal associations between changes in physical activity and depressive symptoms in adulthood: the young Finns study.
abstract: BACKGROUND
  Although previous studies have associated physical activity (PA) with lower depressive symptoms, the combined effects of the (1) frequency, (2) intensity, and (3) duration of long-term PA have not been examined in detail.
  
  
  OBJECTIVE
  We examined the dose-response association between changes in frequency, intensity, and duration of PA and depressive symptoms in men and women over 6 years.
  
  
  METHODS
  Participants comprised 1,959 healthy adults (833 men and 1,126 women), aged 24-39 years in 2001, drawn from the ongoing Young Finns Study. PA was assessed using a self-report questionnaire completed in connection with a medical examination in 2001 and 2007. Depressive symptoms were simultaneously assessed using a modified version of Beck's Depression Inventory in both phases.
  
  
  RESULTS
  High doses of PA at baseline were prospectively associated with fewer depressive symptoms in men, while moderate doses of PA at baseline were inversely associated with the prevalence of depressive symptoms in women. Associations between baseline PA and depressive symptom changes were mediated by social and health-related factors which differed between men and women. Long-term participation in regular PA in all dimensions remained remarkably stable (all p < 0.001). Compared to those who remained inactive, the persistently active participants in all dimensions, with the exception of women's intensity group, were more likely to show decreases in depressive symptoms independent of the included confounders. An increase in PA in certain groups was also independently associated with fewer depressive symptoms, particularly in women.
  
  
  CONCLUSIONS
  Regular and persistent participation in different doses of PA may provide short-term and long-term beneficial effects on depressive symptom changes. The results imply that the moderate to high doses of PA may serve as a buffer against depression in early midlife.
authors.affiliation: LIKES-Research Center for Sport and Health Sciences, Viitaniementie 15a, 40720, Jyväskylä, Finland, xiaolin.yang@likes.fi.
authors.forename: Xiaolin
authors.initials: X
authors.lastname: Yang
authors.forename: Mirja
authors.initials: M
authors.lastname: Hirvensalo
authors.forename: Mirka
authors.initials: M
authors.lastname: Hintsanen
authors.forename: Taina
authors.initials: T
authors.lastname: Hintsa
authors.forename: Laura
authors.initials: L
authors.lastname: Pulkki-Råback
authors.forename: Markus
authors.initials: M
authors.lastname: Jokela
authors.forename: Risto
authors.initials: R
authors.lastname: Telama
authors.forename: Tuija
authors.initials: T
authors.lastname: Tammelin
authors.forename: Nina
authors.initials: N
authors.lastname: Hutri-Kähönen
authors.forename: Jorma S A
authors.initials: JS
authors.lastname: Viikari
authors.forename: Olli T
authors.initials: OT
authors.lastname: Raitakari
mesh_terms: D000328:Adult; D003863:Depression / Q000453:epidemiology*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000502:physiology*; D055815:Young Adult