title: Marijuana use trajectories among drug-using youth presenting to an urban emergency department: Violence and social influences.
abstract: This paper examined longitudinal marijuana use trajectories among drug-using youth presenting to the ED to inform intervention development.
  
  
  
  Given interest in substance use and violence, this study oversampled those presenting with assault injuries. Assault-injured youth (ages 14-24) endorsing past 6-month drug use (n=349), and a sex and age proportionally-sampled comparison group (n=250) endorsing drug use, completed a baseline assessment and follow-ups at 6, 12, 18, and 24 months. Latent class trajectory analyses examined days of marijuana use over 2 years. Multinomial regression analyses examined baseline, 12-month and 24-month factors associated with substance use trajectory groups.
  
  
  
  Trajectory analyses identified 5 groups: Low (Low; 28.2%; n=169); Intermittent (INT; 16.2%; n=97); Moderate Decline (MD; 12.0%; n=72); High decline (HD, 13.2%; n=79) and Chronic (C; 30.4%; n=182). At baseline, as compared to the Low group, the other trajectory groups were more likely to be male and have greater levels of physical aggression. At 12- and 24-months, negative and positive peer influences, incarceration and community violence were additional characteristics associated with the greater marijuana use trajectories (as compared to the Low group).
  
  
  
  Interventions for drug-using youth presenting to the urban ED should address peer influences, physical aggression and community violence exposure, given the association between these characteristics and greater marijuana use trajectories.
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; University of Michigan Addiction Center, Department of Psychiatry, University of Michigan School of Medicine, 4250 Plymouth Road, Ann Arbor, MI 48109, USA. Electronic address: waltonma@umich.edu.
authors.forename: Maureen A
authors.initials: MA
authors.lastname: Walton
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; Institute on Women and Gender Studies, University of Michigan, 500 South State St., Ann Arbor, MI 48109, USA.
authors.forename: Quyen
authors.initials: Q
authors.lastname: Epstein-Ngo
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; Michigan Youth Violence Prevention Center, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA; Department of Emergency Medicine, University of Michigan School of Medicine, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA; Department of Emergency Medicine, Hurley Medical Center, 1 Hurley Plaza, Flint, MI 48503, USA.
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Carter
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; Michigan Youth Violence Prevention Center, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA; Department of Health Behavior and Health Education, University of Michigan School of Public Health, 1415 Washington Heights 3790A SPH I, Ann Arbor, MI 48109, USA.
authors.forename: Marc A
authors.initials: MA
authors.lastname: Zimmerman
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; University of Michigan Addiction Center, Department of Psychiatry, University of Michigan School of Medicine, 4250 Plymouth Road, Ann Arbor, MI 48109, USA.
authors.forename: Frederic C
authors.initials: FC
authors.lastname: Blow
authors.affiliation: Department of Health Behavior and Biological Sciences, University of Michigan School of Nursing, 400 North Ingalls, Room 4346, Ann Arbor, MI 48109, USA.
authors.forename: Anne
authors.initials: A
authors.lastname: Buu
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Goldstick
authors.affiliation: University of Michigan Injury Center, University of Michigan School of Medicine, 2800 Plymouth Road, NCRC10-G080, Ann Arbor, MI 48109, USA; Michigan Youth Violence Prevention Center, University of Michigan School of Public Health, 1415 Washington Heights, Ann Arbor, MI 48109, USA; Department of Emergency Medicine, University of Michigan School of Medicine, 1500 East Medical Center Drive, Ann Arbor, MI 48105, USA; Department of Emergency Medicine, Hurley Medical Center, 1 Hurley Plaza, Flint, MI 48503, USA.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Cunningham
mesh_terms: D000293:Adolescent; D000374:Aggression / Q000523:psychology; D002188:Cannabis; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data*; D005260:Female; D006786:Hospitals, Urban / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology* / Q000523:psychology*; D008385:Marijuana Smoking; D010379:Peer Group; D012307:Risk Factors; D012737:Sex Factors; D012932:Social Facilitation; D019966:Substance-Related Disorders / Q000453:epidemiology* / Q000523:psychology*; D014754:Violence / Q000523:psychology* / Q000706:statistics & numerical data*; D014947:Wounds and Injuries / Q000453:epidemiology* / Q000523:psychology*; D055815:Young Adult
keywords: Latent class trajectory analysis; Marijuana use; Peer influence; Violence; Youth