title: Review of twin and adoption studies of adolescent substance use.
abstract: OBJECTIVE
  To review studies of adolescent substance use and abuse with genetically informative designs.
  
  
  METHODS
  Twin and adoption studies of adolescent substance use were searched in Medline using keywords.
  
  
  RESULTS
  Of 19 studies that used adolescent samples, 18 examined initiation or use of substances and 1 examined abuse. Of the 7 retrospective studies using adult samples, 6 examined problematic behaviors such as substance dependence. Genetic and shared environmental influences on adolescent substance use are moderated by the specific substance, age, gender, specific contexts, religiousness, and region. There is some evidence for a common genetic influence on substance use across substances. Genetic influences on adolescent substance use may act through an influence on disinhibited behavior. Shared environment contributed to adolescent substance use consistently across all adolescent samples and common shared environmental influences influenced initiation into tobacco and alcohol use. While parental alcohol use had a small influence on adolescent shared environment, sibling influences were substantial.
  
  
  CONCLUSIONS
  Twin and adoption studies have increased our understanding of genetic and environmental influences on adolescent substance use and its initiation; however, more studies focusing on clinical syndromes of abuse and dependence are needed.
authors.affiliation: Division of Substance Dependence, Department of Psychiatry, University of Colorado Health Sciences Center, Denver, USA. Christian.Hopfer@uchsc.edu
authors.forename: Christian J
authors.initials: CJ
authors.lastname: Hopfer
authors.forename: Thomas J
authors.initials: TJ
authors.lastname: Crowley
authors.forename: John K
authors.initials: JK
authors.lastname: Hewitt
mesh_terms: D000293:Adolescent; D000300:Adoption; D000428:Alcohol Drinking / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D012907:Smoking / Q000235:genetics; D019966:Substance-Related Disorders / Q000235:genetics*; D014427:Twins / Q000235:genetics*