title: Solitary cannabis use in adolescence as a correlate and predictor of cannabis problems.
abstract: BACKGROUND
  Most adolescent cannabis use occurs in social settings among peers. Solitary cannabis use during adolescence may represent an informative divergence from normative behavior with important implications for understanding risk for cannabis problems. This longitudinal study examined associations of adolescent solitary cannabis use with levels of cannabis use and problems in adolescence and in young adulthood.
  
  
  METHODS
  Cannabis using-adolescents aged 12-18 were recruited from clinical programs (n=354; 43.8% female; 83.3% Caucasian) and community sources (n=93; 52.7% female; 80.6% Caucasian). Participants reported on cannabis use patterns and diagnostic symptoms at baseline and multiple follow-ups into young adulthood.
  
  
  RESULTS
  Compared to social-only users, adolescent solitary cannabis users were more likely to be male and reported more frequent cannabis use and more DSM-IV cannabis use disorder (CUD) symptoms. Regression analyses showed that solitary cannabis use in adolescence predicted CUD symptom counts in young adulthood (age 25) after controlling for demographic variables and the frequency of adolescent cannabis use. However, solitary adolescent cannabis use was no longer predictive of age 25 CUD symptoms after additionally controlling for adolescent CUD symptoms.
  
  
  CONCLUSIONS
  Solitary cannabis use is associated with greater cannabis use and problems during adolescence, but evidence is mixed that it predicts young adult cannabis problems.
authors.affiliation: Department of Psychology, Carnegie Mellon University, Pittsburgh, PA, USA. Electronic address: kasey@andrew.cmu.edu.
authors.forename: Kasey G
authors.initials: KG
authors.lastname: Creswell
authors.affiliation: Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Tammy
authors.initials: T
authors.lastname: Chung
authors.affiliation: Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Duncan B
authors.initials: DB
authors.lastname: Clark
authors.affiliation: Department of Psychiatry, University of Pittsburgh, Pittsburgh, PA, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Martin
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior; D000328:Adult; D002188:Cannabis; D039721:Diagnostic and Statistical Manual of Mental Disorders; D018450:Disease Progression; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D002189:Marijuana Abuse; D008385:Marijuana Smoking; D012044:Regression Analysis; D012306:Risk; D012737:Sex Factors; D012919:Social Behavior; D055815:Young Adult
keywords: Adolescence; Cannabis use disorder; Longitudinal; Solitary marijuana use; Solitary use