title: Longitudinal trajectories of marijuana use from adolescence to young adulthood.
abstract: BACKGROUND
  Marijuana use is increasingly widespread among adolescents and young adults; however, few studies have examined longitudinal trajectories of marijuana use during this important developmental period. As such, we examined adolescent trajectories of marijuana use and the psychosocial factors that may differentiate individuals who escalate their marijuana use over adolescence and young adulthood from those who do not.
  
  
  METHODS
  Participants were 1204 9th and 10th graders at baseline who were over-sampled for cigarette use and were followed over 6-years, as part of an extensive longitudinal study, the Social and Emotional Contexts of Adolescent Smoking Patterns (SECASP) study. Growth Mixture Modeling (GMM) was used to model trajectories of marijuana use and Mixed Effects Regression analyses were used to examine psychosocial correlates of marijuana use escalation over time.
  
  
  RESULTS
  Our results revealed three trajectories of non-escalating users (low users, medium users, and high users) and one escalating user trajectory. We found that relative to Non-escalators the Escalators had higher cigarette smoking (p<.0001), novelty-seeking (p=.02), aggressive and anti-social behavior (p<.007), and problem behavior related to peer context (p=.04). Moreover, there were important time and Group by Time interactions in some of these relationships. On the other hand, parental control and depression did not differ between escalators and low and medium non-escalating users.
  
  
  CONCLUSIONS
  Cigarette smoking, novelty-seeking, aggressive and anti-social behavior, and peer influence are related to 'escalating' marijuana use throughout adolescence and young adulthood.
authors: Department of Psychiatry, University of Illinois at Chicago, Chicago, IL, USA; Institute for Juvenile Research, University of Illinois at Chicago, Chicago, IL, USA.
authors: A M
authors: AM
authors: Passarotti
authors: Institute for Health Research and Policy, University of Illinois at Chicago, Chicago, IL, USA; Department of Psychology, University of Illinois at Chicago, Chicago, IL, USA.
authors: Natania A
authors: NA
authors: Crane
authors: Institute for Health Research and Policy, University of Illinois at Chicago, Chicago, IL, USA; Division of Epidemiology and Biostatistics, University of Illinois at Chicago, Chicago, IL, USA.
authors: Donald
authors: D
authors: Hedeker
authors: Institute for Health Research and Policy, University of Illinois at Chicago, Chicago, IL, USA; Department of Psychology, University of Illinois at Chicago, Chicago, IL, USA.
authors: Robin J
authors: RJ
authors: Mermelstein
mesh_terms: D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D000374:Aggression / Q000523:psychology*; D000987:Antisocial Personality Disorder / Q000453:epidemiology / Q000523:psychology; D015331:Cohort Studies; D003863:Depression / Q000453:epidemiology / Q000523:psychology; D018450:Disease Progression; D005106:Exploratory Behavior; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology / Q000523:psychology*; D008385:Marijuana Smoking / Q000453:epidemiology / Q000523:psychology*; D010379:Peer Group; D011446:Prospective Studies; D012307:Risk Factors; D012907:Smoking / Q000453:epidemiology / Q000523:psychology*; D012925:Social Conformity; D012931:Social Environment; D013315:Stress, Psychological / Q000453:epidemiology / Q000523:psychology; D013694:Temperament; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: Adolescence; Longitudinal trajectories; Marijuana use; Psychosocial