title: Are Changes in Alcohol Consumption Among Swedish Youth Really Occurring 'in Concert'? A New Perspective Using Quantile Regression.
abstract: OBJECTIVE
  Recent studies of youth alcohol consumption indicate a collective downward drinking trend at all levels of consumption, i.e. reductions occurring 'in concert'. We re-examine the collectivity of drinking theory by applying quantile regression methods to the analysis and interpretation of Swedish youth alcohol consumption.
  
  
  METHODS
  Changes in youth alcohol consumption between 2000 and 2014 were assessed using a school-based survey conducted in Stockholm (n = 86,402). Participants were Swedish youth aged 15-18 years. The rate of change in consumption was examined using quantile regression, and compared to Ordinary Least Squares modelling. The hypothesis of parallelism or 'in concert' changes in consumption was assessed using the test of the equality of linear regression slopes corresponding to different quantiles of log consumption.
  
  
  RESULTS
  In both models, changes in consumption over time did not occur in parallel, contrary to the collectivity of drinking theory. Instead, a clear divergence in the rate of drinking was observed, with most adolescent quantiles reducing consumption, while heavy consuming remained stable.
  
  
  CONCLUSIONS
  Contrary to previous studies, our findings do not support a collectivity of drinking behaviour among Swedish youth. Quantile regression is a robust and appropriate method for analysing temporal changes in alcohol consumption data.
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Solnavägen 1, 171 77, Stockholm, Sweden.
authors.forename: Zangin
authors.initials: Z
authors.lastname: Zeebari
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Solnavägen 1, 171 77, Stockholm, Sweden.
authors.forename: Andreas
authors.initials: A
authors.lastname: Lundin
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Solnavägen 1, 171 77, Stockholm, Sweden.
authors.forename: Paul W
authors.initials: PW
authors.lastname: Dickman
authors.affiliation: Department of Public Health Sciences, Karolinska Institutet, Solnavägen 1, 171 77, Stockholm, Sweden.
authors.forename: Mats
authors.initials: M
authors.lastname: Hallgren
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D011582:Psychological Theory; D012044:Regression Analysis; D013548:Sweden / Q000453:epidemiology; D000066608:Underage Drinking / Q000639:trends*