title: Naturally occurring changes in physical activity are inversely related to depressive symptoms during early adolescence.
abstract: OBJECTIVE
  We examined the relationship between naturally occurring changes in physical activity and depressive symptoms across a 2-year period among adolescent boys and girls.
  
  
  METHODS
  Participants (N = 4594) reported their frequency of physical activity outside of school and completed the Center for Epidemiological Studies Depression scale in the Fall of 1998 (beginning of 7th grade; baseline data), Spring of 1999 (end of 7th grade; interim data), and Spring of 2000 (end of 8th grade; follow-up data).
  
  
  RESULTS
  Latent growth modeling indicated that a 1 SD unit change in the frequency of leisure-time physical activity was inversely related to a.25 SD unit change in depressive symptoms. This relationship was attenuated but remained statistically significant when simultaneously controlling for the confounding variables of sex, socioeconomic status, smoking, alcohol consumption, and the value participants placed on their health, appearance, and achievement.
  
  
  CONCLUSIONS
  Naturally occurring changes in physical activity were negatively related with changes in depressive symptoms. The results encourage randomized controlled trials to experimentally determine whether an increase in physical activity reduces depression risk among adolescent boys and girls.
authors.affiliation: Department of Exercise Science, The University of Georgia, Athens, Georgia 30602-6554, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Motl
authors.forename: Amanda S
authors.initials: AS
authors.lastname: Birnbaum
authors.forename: Martha Y
authors.initials: MY
authors.lastname: Kubik
authors.forename: Rod K
authors.initials: RK
authors.lastname: Dishman
mesh_terms: D000124:Achievement; D000293:Adolescent; D000294:Adolescent Behavior / Q000502:physiology; D000428:Alcohol Drinking / Q000453:epidemiology / Q000523:psychology; D001294:Attitude to Health; D015897:Comorbidity; D015986:Confounding Factors, Epidemiologic; D003866:Depressive Disorder / Q000175:diagnosis* / Q000453:epidemiology / Q000523:psychology; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D009043:Motor Activity / Q000502:physiology*; D010555:Personality Inventory; D011569:Psychiatric Status Rating Scales; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology / Q000523:psychology; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires