title: Modelling possible causality in the associations between unemployment, cannabis use, and alcohol misuse.
abstract: There has been considerable interest in the extent to which substance use and unemployment may be related, particularly the causal pathways that may be involved in these associations. It has been argued that these associations may reflect social causation, in which unemployment influences substance use, or that they may reflect social selection, in which substance use increases the risk of becoming and remaining unemployed. The present study sought to test these competing explanations.
  
  
  
  Data from the Christchurch Health and Development Study, featuring a longitudinal birth cohort, were used to model the associations between unemployment and both cannabis and alcohol. Data on patterns of unemployment, involvement with cannabis, and symptoms of alcohol use disorder were examined from ages 18-35 years. The associations between unemployment and both cannabis dependence and alcohol use disorder (AUD) were modelled using conditional fixed-effects regression models, augmented by time-dynamic covariate factors.
  
  
  
  The analyses showed evidence of possible reciprocal causal processes in the association between unemployment and cannabis dependence, in which unemployment of at least three months' duration significantly (p < 0.0001) increased the risk of cannabis dependence, and cannabis dependence significantly (p < 0.0001) increased the risk of being unemployed. Similar evidence was found for the associations between unemployment and AUD, although these associations were smaller in magnitude.
  
  
  
  The present findings support both social causation and social selection arguments, by indicating that unemployment plays a causal role in substance misuse, and that it is also likely that a reverse causal process whereby substance misuse increases the risk of unemployment.
authors.affiliation: Christchurch Health and Development Study, Department of Psychological Medicine, University of Otago, Christchurch, New Zealand. Electronic address: joseph.boden@otago.ac.nz.
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Boden
authors.affiliation: School of Social Work, University of Southern California, Los Angeles, CA, USA.
authors.forename: Jungeun Olivia
authors.initials: JO
authors.lastname: Lee
authors.affiliation: Christchurch Health and Development Study, Department of Psychological Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: L John
authors.initials: LJ
authors.lastname: Horwood
authors.affiliation: School of Social Work, University of Southern California, Los Angeles, CA, USA.
authors.forename: Carolina Villamil
authors.initials: CV
authors.lastname: Grest
authors.affiliation: Christchurch Health and Development Study, Department of Psychological Medicine, University of Otago, Christchurch, New Zealand.
authors.forename: Geraldine F H
authors.initials: GF
authors.lastname: McLeod
mesh_terms: D000293:Adolescent; D000328:Adult; D000428:Alcohol Drinking; D019973:Alcohol-Related Disorders / Q000453:epidemiology*; D002188:Cannabis; D015984:Causality; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D010379:Peer Group; D012307:Risk Factors; D019966:Substance-Related Disorders / Q000453:epidemiology*; D014478:Unemployment / Q000706:statistics & numerical data*; D055815:Young Adult
keywords: Alcohol use disorder; Cannabis use; Longitudinal study; Unemployment