title: A systematic evaluation and validation of subtypes of adolescent alcohol use motives: genetic and environmental contributions.
abstract: BACKGROUND
  Alcohol use motives are closely associated with specific profiles of alcohol use and reflect a subjectively derived decisional framework based on a motivational style of responding. Adult twin studies typically estimate the heritability of alcohol use motives to be between 7 and 42%, although relatively little is known about genetic and environmental influences upon alcohol use motives in adolescence.
  
  
  METHODS
  Latent class analysis (LCA) models containing 1 through 5 classes were fitted to the data derived from 1,422 adolescent twin and siblings self-reported alcohol use motives. Using twin models, we estimated the genetic, shared, and nonshared environmental influences to the class membership data derived from the LCA.
  
  
  RESULTS
  Four drinking motives classes were identified (family-oriented, social, enhancement/social, and coping/social). The coping/social and enhancement/social classes were differentiated from the social class on measures of depression, delinquency, and aggressive behavior. Analyses indicated that nonadditive genetic factors accounted for 76% of the variance in the coping/social motives class and additive genetic influences accounted for 66% of the variance in the social motives class. There was a moderate contribution of genetic factors and shared environmental factors influencing class membership of enhancement/social motivated drinkers (28 and 20% explained variance, respectively). Substantial shared environmental influences were revealed for membership of the family-oriented class (75%).
  
  
  CONCLUSIONS
  Heritable influences may predispose individuals to drink to cope with negative affect, for social reasons, and to a lesser extent for enhancement. Familial environmental influences shape family-oriented motives for drinking in adolescents.
authors.affiliation: Division of Psychological Medicine and Psychiatry, Addictions Department, Institute of Psychiatry, Kings' College London, UK. clare.mackie@kcl.ac.uk
authors.forename: Clare J
authors.initials: CJ
authors.lastname: Mackie
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: Conrod
authors.forename: Fruhling
authors.initials: F
authors.lastname: Rijsdijk
authors.forename: Thalia C
authors.initials: TC
authors.lastname: Eley
mesh_terms: D000223:Adaptation, Psychological / Q000502:physiology; D000293:Adolescent; D000294:Adolescent Behavior / Q000502:physiology / Q000523:psychology*; D000367:Age Factors; D000428:Alcohol Drinking / Q000453:epidemiology / Q000235:genetics* / Q000523:psychology*; D002648:Child; D005190:Family; D005260:Female; D006801:Humans; D008297:Male; D009042:Motivation / Q000235:genetics*; D011897:Random Allocation; D057566:Self Report; D012931:Social Environment; D055815:Young Adult