title: Polysubstance use, mental health and high-risk behaviours: Results from the 2012 Global Drug Survey.
abstract: OBJECTIVE
  Polysubstance use is associated with adverse health and social outcomes, but few studies have investigated whether these associations differ between individuals engaged in different patterns of illicit drug and non-prescription medication use.
  
  
  METHODS
  Latent class analysis (LCA) was used to identify patterns of drug use in the Global Drug Survey, a purposive sample collected in late 2012 and surveyed using an online questionnaire including past-year drug use, sociodemographics, mental illness, involvement in violence and sexual behaviour. The sample analysed (n = 14, 869; median age 27 years; 68.5% male) included those residing in the UK (n = 5869), Australia (n = 6313) and the USA (n = 2687).
  
  
  RESULTS
  LCA of cannabis, ecstasy, cocaine, stimulants, nitrous, ketamine, benzodiazepines and opioid painkiller use identified six classes: no polysubstance use (Class 1, 49.1%); cannabis and ecstasy (Class 2, 23.6%); all illicit drugs (Class 3, 9.4%); ecstasy and cocaine (Class 4, 8.3%); cannabis and medication (Class 5, 5.9%); and all drugs (Class 6, 3.8%). Participants diagnosed with anxiety were most likely to belong to Class 5 [odds ratio (OR) 2.66, 95% confidence interval (CI) 2.10-3.38]. Violent behaviour was most strongly associated with Class 6 membership (OR 1.9, 95% CI 1.36-2.64). Sexual risk-taking also predicted membership of this class (OR 5.79, 95% CI 4.66-7.18) and Class 4 (OR 4.41, 95% CI 3.57-5.43).
  
  
  CONCLUSIONS
  Five heterogeneous groups of polysubstance users were identified in this international sample covering the UK, Australia and USA. Anxiety disorders were associated with medication and cannabis use, while high-risk behaviours predicted use of cocaine and ecstasy, or wide-ranging polysubstance use including ketamine and medications.
authors: National Addictions Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.|Clinical Epidemiology, Farr Institute for Health Informatics Research, University College London, London, UK.|Centre for Molecular, Environmental, Genetic and Analytic Epidemiology, Melbourne School of Global and Population Health, The University of Melbourne, Melbourne, Australia.
authors: Katherine I
authors: KI
authors: Morley
authors: National Addictions Centre, Institute of Psychiatry, Psychology & Neuroscience, King's College London, London, UK.
authors: Michael T
authors: MT
authors: Lynskey
authors: Health Services and Population Research Department, Institute of Psychiatry, Psychology, & Neuroscience, King's College London, London, UK.
authors: Paul
authors: P
authors: Moran
authors: Centre for Adolescent Health, Murdoch Children's Research Institute, University of Melbourne, Royal Children's Hospital, Melbourne, Australia.
authors: Rohan
authors: R
authors: Borschmann
authors: South London and Maudsley NHS Trust/King's College London, London, UK.|Global Drug Survey, London, UK.
authors: Adam R
authors: AR
authors: Winstock
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia / Q000453:epidemiology; D005260:Female; D006801:Humans; D013287:Illicit Drugs / Q000009:adverse effects; D008297:Male; D001523:Mental Disorders / Q000453:epidemiology*; D008603:Mental Health; D008875:Middle Aged; D012309:Risk-Taking; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D019966:Substance-Related Disorders / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D006113:United Kingdom / Q000453:epidemiology; D014481:United States / Q000453:epidemiology; D014754:Violence / Q000706:statistics & numerical data*; D055815:Young Adult
chemical_list: D013287:Illicit Drugs
keywords: comorbidity; epidemiology; latent class analysis; polysubstance; psychopathology