Studies to date showing an association between cannabis use and schizophrenia-spectrum disorders are of relatively small sample sizes with limitations in generalizability. The present study addresses this gap by examining the relationship between cannabis use and psychotic-like symptoms in a large representative community sample.
Data were derived from the 2004 – 2005 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC, Wave 2), a large, nationally representative sample of 34 653 adults from the United States population. We evaluated the association between lifetime cannabis use, psychosis, and schizotypal personality features.
The prevalence of psychosis and schizotypal personality disorder increased significantly with greater cannabis use in a dose-dependent manner. The association between cannabis use and psychosis was 1.27 (95% CI 1.03–1.57) for lifetime cannabis use, 1.79 (95% CI 1.35–2.38) for lifetime cannabis abuse, and 3.69 (95% CI 2.49–5.47) for lifetime cannabis dependence. There was a similar dose-response relationship between the extent of cannabis use and schizotypal personality disorder (OR = 2.02 for lifetime cannabis use, 95% CI 1.69–2.42; OR = 2.83 for lifetime cannabis abuse, 95% CI 2.33–2.43; OR = 7.32 for lifetime cannabis dependence, 95% CI 5.51–9.72). Likelihood of individual schizotypal features increased significantly with increased extent of cannabis use in a dose-dependent manner.
This is the first population-based study to examine the association between lifetime cannabis use, psychosis, and schizotypal personality traits. These results add to evidence that cannabis use may be a risk factor for psychosis liability.
Read full study here