title: Tests of the effects of adolescent early alcohol exposures on adult outcomes.
abstract: OBJECTIVE
  To determine whether early adolescent alcohol use contributes to adult alcohol use, misuse and other adult substance-related and social outcomes.
  
  
  METHODS
  In a longitudinal study of twins assessed at target ages 11, 14 and 24 years, two techniques adjusted for confounding factors: a propensity score (PS) adjusting for the effects of measured background covariates and co-twin control (CTC) adjusting for confounding by unmeasured (including genetic) factors shared within early alcohol exposure-discordant pairs.
  
  
  METHODS
  The community-based Minnesota Twin Family Study.
  
  
  METHODS
  A total of 1512 (50.3% female) twins.
  
  
  METHODS
  Early adolescent alcohol exposures, adult substance-related and social outcomes and background variables reflecting behavioral, familial and environmental characteristics.
  
  
  RESULTS
  Background covariates unbalanced between those with and without early alcohol exposure were balanced through PS-based weighting, leaving several adult outcomes related to substance use or social functioning remaining significantly associated with early alcohol exposure. Similarly, the within-pair individual-level component of a CTC indicated that early alcohol-exposed twins had higher risk than their non-exposed co-twins for several, but not all, of the same adult outcomes. For example, early alcohol use was associated with an adult index of alcohol use in both PS-weighted (β = 0.57, P < 0.001) and CTC (β = 0.21, P = 0.031) analyses.
  
  
  CONCLUSIONS
  Early alcohol exposures predict adult alcohol problems and related outcomes, despite stringent adjustment for measured and non-measured sources of potential confounding using propensity score and co-twin control. Contrasting the methods indicated that exposure effect estimates from PS application were likely biased by unmeasured confounding factors.
authors.affiliation: Department of Psychology, University of Minnesota, Minneapolis, MN, USA.
authors.forename: Daniel E
authors.initials: DE
authors.lastname: Irons
authors.forename: William G
authors.initials: WG
authors.lastname: Iacono
authors.forename: Matt
authors.initials: M
authors.lastname: McGue
mesh_terms: D000293:Adolescent; D017668:Age of Onset; D019973:Alcohol-Related Disorders / Q000453:epidemiology / Q000209:etiology / Q000235:genetics; D000435:Alcoholic Intoxication / Q000453:epidemiology / Q000235:genetics / Q000523:psychology; D002648:Child; D004777:Environment; D005195:Family Relations / Q000523:psychology; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000453:epidemiology / Q000209:etiology* / Q000235:genetics; D014429:Twins, Dizygotic / Q000523:psychology; D014430:Twins, Monozygotic / Q000523:psychology; D000066608:Underage Drinking / Q000523:psychology*; D055815:Young Adult
keywords: Adolescence; alcohol; causality; co-twin control; longitudinal; propensity score; twins