title: Mode of daily caffeine consumption among adolescents and the practice of mixing alcohol with energy drinks: relationships to drunkenness.
abstract: OBJECTIVE
  Adolescent use of alcohol mixed with energy drinks (AmED) has recently received increased attention. Previous studies have established a strong link between AmED and drunkenness and suggest the importance of understanding associations with AmED use. In this study, we operationalized caffeine as daily consumption of coffee, tea, cola drinks, and energy drinks, and examined whether daily caffeine consumption relates to AmED use and drunkenness.
  
  
  METHODS
  We used multilevel structural equation modeling (SEM) with data from the 2013 Youth in Iceland cross-sectional survey among students, ages 16-17 years, who attended all of Iceland's 31 junior colleges (N = 5,784; 75% response rate; 51% girls).
  
  
  RESULTS
  Our primary model fit the data very well with a comparative fit index of .994 and root mean square error of approximation of .042. Of the four daily caffeine consumption variables, coffee had the strongest relationship with AmED for both girls and boys, followed by energy drink consumption. The direct relationship between the daily caffeine consumption variables and drunkenness was generally weak for both genders, but the majority of the total relationship between all daily caffeine consumption variables and drunkenness was attributable to mediation through AmED. In our primary model, AmED consumption was also very strongly related to drunkenness (standardized βs = .74-.79).
  
  
  CONCLUSIONS
  Caffeine use among adolescents ages 16-17 years is strongly related to increased consumption of AmED, irrespective of mode of caffeine consumption. AmED is strongly and positively associated with drunkenness on both individual and school levels.
authors.affiliation: Department of Social and Behavioral Sciences, West Virginia University, School of Public Health, Morgantown, West Virginia.|Icelandic Centre for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.
authors.forename: Alfgeir L
authors.initials: AL
authors.lastname: Kristjansson
authors.affiliation: Department of Social and Behavioral Sciences, West Virginia University, School of Public Health, Morgantown, West Virginia.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Mann
authors.affiliation: Icelandic Centre for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.|Department of Health & Behavior Studies, Teachers College, Columbia University, New York, New York.|Department of Psychology, Reykjavik University, Reykjavik, Iceland.
authors.forename: Inga Dora
authors.initials: ID
authors.lastname: Sigfusdottir
authors.affiliation: Icelandic Centre for Social Research and Analysis, Reykjavik University, Reykjavik, Iceland.|Department of Psychology, Reykjavik University, Reykjavik, Iceland.
authors.forename: Jack E
authors.initials: JE
authors.lastname: James
mesh_terms: D000293:Adolescent; D000434:Alcoholic Beverages; D000435:Alcoholic Intoxication / Q000453:epidemiology*; D002110:Caffeine / Q000008:administration & dosage*; D003430:Cross-Sectional Studies; D061215:Energy Drinks; D000431:Ethanol / Q000008:administration & dosage*; D005260:Female; D006801:Humans; D008297:Male; D012574:Schools; D013334:Students / Q000706:statistics & numerical data
chemical_list: D002110:Caffeine; D000431:Ethanol