title: Population trends in smoking, alcohol use and primary prevention variables among adolescents in Iceland, 1997-2014.
abstract: OBJECTIVE
  To estimate linear time-trends in substance use and primary prevention variables in adolescents in Iceland from 1997 to 2014.
  
  
  METHODS
  Repeated, cross-sectional population-based school surveys with seven waves of pooled data.
  
  
  METHODS
  Iceland.
  
  
  METHODS
  All accessible students enrolled in the 9th and 10th grades in the national Icelandic school system during the spring of 1997, 2000, 2003, 2006, 2009, 2012 and 2014 (n = 50 412, boys = 50%). Response rates ranged between 81 and 90% of the population.
  
  
  METHODS
  Measures on substance use included smoking and alcohol use. Primary prevention measures included parental monitoring, parental social involvement, participation in organized sports and reduced participation in a party life-style.
  
  
  RESULTS
  Substance use decreased consistently during the study period. For example, 30-day drunkenness declined from 29.6 in 1997 to 3.6% in 2014 (linear trend: χ(2) (1)  = 2846.8, P < 0.001), and daily smoking during the last 30 days declined from 17.0 to 1.6% during the same period (linear trend: χ(2) (1)  = 1614.3, P < 0.001). Primary prevention factors strengthened over time. For example, the mean score for parents knowing where their children are in the evenings rose from 2.44 in 1997 to 3.08 in 2014 (Ftrend(1, 42635) , 2538.3, P < 0.001), and mean scores for participation in party life-style declined from 2.23 in 1997 to 1.71 in 2014 (Ftrend(1, 38773) , 2033.1, P < .001).
  
  
  CONCLUSIONS
  Substance use among adolescents in Iceland has declined steadily from 1997 to 2014, while primary prevention factors for substance use have increased in strength during the same time-period.
authors.affiliation: Department of Social and Behavioral Sciences, School of Public Health, West Virginia University, Morgantown, WV, USA.|Icelandic Center for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.
authors.forename: Alfgeir L
authors.initials: AL
authors.lastname: Kristjansson
authors.affiliation: Icelandic Center for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.|Department of Psychology, Reykjavik University, Reykjavik, Iceland.|Department of Health and Behavior Studies, Teachers College, Columbia University, New York, NY, USA.
authors.forename: Inga Dora
authors.initials: ID
authors.lastname: Sigfusdottir
authors.affiliation: Faculty of Social Sciences, University of Iceland, Reykjavik, Iceland.
authors.forename: Thorolfur
authors.initials: T
authors.lastname: Thorlindsson
authors.affiliation: Department of Social and Behavioral Sciences, School of Public Health, West Virginia University, Morgantown, WV, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mann
authors.affiliation: Icelandic Center for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.
authors.forename: Jon
authors.initials: J
authors.lastname: Sigfusson
authors.affiliation: Department of Health and Behavior Studies, Teachers College, Columbia University, New York, NY, USA.|Mailman School of Public Health, Columbia University, New York, NY, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Allegrante
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D008297:Male; D011322:Primary Prevention / Q000379:methods*; D012907:Smoking / Q000453:epidemiology*; D000066608:Underage Drinking / Q000706:statistics & numerical data*
keywords: Adolescents; Iceland; alcohol use; primary prevention; smoking; substance use