title: The association between substance use disorders and early and combined use of alcohol and marijuana in two American Indian populations.
abstract: OBJECTIVE
  To study the relationships between early and combined use of alcohol and marijuana with diagnoses of alcohol and marijuana use disorders in two American Indian (AI) populations.
  
  
  METHODS
  Data were drawn from a psychiatric epidemiologic study of 3084 AIs living on or near two reservations. We analysed data for adults aged 18-54 years at the time of interview (n= 2739). Logistic regression models were estimated to examine associations between early and combined use of alcohol and marijuana with lifetime diagnoses of abuse and dependence.
  
  
  RESULTS
  Overall, younger AIs (18-29 years old) were more likely than older AIs (40-54 years old) to initiate substance use early and initiate use with marijuana, with or without alcohol. Persons who initiated alcohol use before age 14 were more than twice as likely as those who initiated use at older ages to meet criteria for alcohol or marijuana use disorders (p< 0.01). The odds of abuse or dependence were two to five times higher among persons who reported combined use of alcohol and marijuana (p< 0.01) than among those who reported use of either substance.
  
  
  CONCLUSIONS
  These findings document the need to address both early and combined use of alcohol and marijuana in prevention and treatment programmes.
authors.affiliation: Centers for American Indian and Alaska Native Health, Colorado School of Public Health, University of Colorado Denver, Aurora, CO, USA.
authors.forename: Joan M
authors.initials: JM
authors.lastname: O'Connell
authors.affiliation: Centers for American Indian and Alaska Native Health, Colorado School of Public Health, University of Colorado Denver, Aurora, CO, USA.
authors.forename: Douglas K
authors.initials: DK
authors.lastname: Novins
authors.affiliation: Centers for American Indian and Alaska Native Health, Colorado School of Public Health, University of Colorado Denver, Aurora, CO, USA.
authors.forename: Janette
authors.initials: J
authors.lastname: Beals
authors.affiliation: Centers for American Indian and Alaska Native Health, Colorado School of Public Health, University of Colorado Denver, Aurora, CO, USA.
authors.forename: Nancy R
authors.initials: NR
authors.lastname: Whitesell
authors.affiliation: Center for Applied Social Research, University of Oklahoma, Norman, OK, USA.
authors.forename: Paul
authors.initials: P
authors.lastname: Spicer
keywords: American Indians; alcohol; marijuana