title: Substance use initiation: the role of simultaneous polysubstance use.
abstract: OBJECTIVE
  Simultaneous polysubstance use (SPU) is a common phenomenon, yet little is known about its role in substance use initiation.
  
  
  METHODS
  In the present study, 226 cannabis users completed structured interviews about their substance use history. For each substance ever used, participants provided details of their age of first use, their use in the preceding 30 days and whether they co-administered any other licit or illicit substances the first time they used the substance.
  
  
  RESULTS
  For most illicit substances [powder cocaine, crack, amphetamine, methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA; ecstasy), heroin, opium, gamma-hydroxybutyric acid (GHB), ketamine, psilocybin (magic mushrooms), mescaline, phencyclidine (PCP), peyote and inhalants], results showed that a clear majority of participants (≥75%) reported SPU during their first-ever use of the substance. While SPU was less common on occasions of first use of alcohol, tobacco and cannabis, a high proportion of SPU on occasions of first use of 'harder' drugs could be accounted for by the co-use of alcohol, tobacco and/or cannabis.
  
  
  CONCLUSIONS
  Such findings raise the possibility that specific alcohol, tobacco and/or cannabis use episodes might directly contribute to the initiation of new substance use. Understanding the role of SPU on occasions of first use might help better identify risk factors for substance use progression and improve intervention efforts.
authors.affiliation: Department of Psychology, Dalhousie University, Halifax, Canada.
authors.forename: Janine V
authors.initials: JV
authors.lastname: Olthuis
authors.forename: Christine
authors.initials: C
authors.lastname: Darredeau
authors.forename: Sean P
authors.initials: SP
authors.lastname: Barrett
mesh_terms: D000293:Adolescent; D000328:Adult; D005260:Female; D006801:Humans; D013287:Illicit Drugs; D008297:Male; D002189:Marijuana Abuse / Q000175:diagnosis / Q000453:epidemiology*; D008875:Middle Aged; D009674:Nova Scotia / Q000453:epidemiology; D063487:Prescription Drug Misuse; D019966:Substance-Related Disorders / Q000175:diagnosis / Q000453:epidemiology; D055815:Young Adult
chemical_list: D013287:Illicit Drugs