title: A model to determine the likely age of an adolescent's first drink of alcohol.
abstract: OBJECTIVE
  With the use of a new cohort of adolescent subjects, predictors from the Semi-Structured Assessment for the Genetics of Alcoholism (SSAGA) interview and the Achenbach Youth Self Report (YSR) were combined to model age of first drink (AFD).
  
  
  METHODS
  Subjects consisted of 820 adolescents (ages 14-17) drawn from the current phase of the Collaborative Study on the Genetics of Alcoholism. Three Cox proportional hazards models were considered. Model 1 contained SSAGA variables equivalent to AFD predictors from our previous study: interview age, family history of alcohol dependence, and number of conduct disorder symptoms. Model 2 incorporated 2 additional SSAGA questions (best friends drink and smoked a cigarette before a reported AFD) plus 8 YSR-derived scale scores. Model 3 was a reduced version of model 2, retaining only significant predictors.
  
  
  RESULTS
  Model 2 was a significant improvement over model 1. Model 3 was the best and the most parsimonious of the 3 with respect to likelihood ratio and Wald χ(2) tests and retained only 5 variables from model 2. Included variables were the following: (1) best friends drink, (2) membership in a high-risk alcohol dependence family, (3) number of conduct disorder symptoms, (4) YSR externalizing score, and (5) YSR social problems score.
  
  
  CONCLUSIONS
  Adding variables to those from our original study improved our ability to model the likely age of alcohol initiation. In addition to the SSAGA, the YSR appears to have utility as a research tool to predict the age of alcohol initiation.
authors.affiliation: Department of Psychiatry, University of Iowa Carver College of Medicine, 200 Hawkins Dr, RM 1873 JPP, Iowa City, IA 52242, USA. samuel-kuperman@uiowa.edu
authors.forename: Samuel
authors.initials: S
authors.lastname: Kuperman
authors.forename: Grace
authors.initials: G
authors.lastname: Chan
authors.forename: John R
authors.initials: JR
authors.lastname: Kramer
authors.forename: Leah
authors.initials: L
authors.lastname: Wetherill
authors.forename: Kathleen K
authors.initials: KK
authors.lastname: Bucholz
authors.forename: Danielle
authors.initials: D
authors.lastname: Dick
authors.forename: Victor
authors.initials: V
authors.lastname: Hesselbrock
authors.forename: Bernice
authors.initials: B
authors.lastname: Porjesz
authors.forename: Madhavi
authors.initials: M
authors.lastname: Rangaswamy
authors.forename: Marc
authors.initials: M
authors.lastname: Schuckit
mesh_terms: D000124:Achievement; D000293:Adolescent; D017668:Age of Onset; D000428:Alcohol Drinking / Q000453:epidemiology* / Q000235:genetics; D000437:Alcoholism / Q000453:epidemiology* / Q000235:genetics / Q000517:prevention & control; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000235:genetics; D002605:Character; D002648:Child; D015897:Comorbidity; D019955:Conduct Disorder / Q000453:epidemiology / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006306:Health Surveys; D006801:Humans; D007389:Internal-External Control; D007406:Interview, Psychological; D016013:Likelihood Functions; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology / Q000235:genetics; D010379:Peer Group; D016016:Proportional Hazards Models; D012307:Risk Factors; D057566:Self Report; D012907:Smoking / Q000453:epidemiology / Q000235:genetics; D012917:Social Adjustment; D012932:Social Facilitation; D014481:United States