Examining the Association Between Cannabis Use and Psychosis after Vermont 2018 Change in Marijuana Legislation

On July 1, 2018 legislation was passed in Vermont which made the recreational possession and cultivation of restricted amounts of cannabis legal for citizens 21 and older. Despite this legislation there is a growing body of evidence suggesting an association between cannabis use and adverse mental health outcomes, specifically psychosis. This study aimed to determine if there was an increased incidence of cannabis use among patients admitted for psychosis in the year after the passage of the 2018 legislation in comparison to the prior year. Retrospective chart review was conducted to identify all patients admitted to the University of Vermont Medical Center during the two-year time period (7/1/2017-7/1/2019) with an ICD-10 code at discharge indicating psychotic illness (n=315). All urine drug screen (UDS) results from these patients during the study window were reviewed to determine drug use. Other descriptive statistics were also gathered and analyzed. Using Fisher’s exact test the number of cannabis positive UDS in the year pre-legislation (n= 52, 38%) and post-legislation (n=89, 45%) were compared (p=0.22). The post-legislation period was associated with a non-significant increase in probability of cannabis use (t=1.33, p=0.19) after adjusting for some patients having multiple admissions. Limitations included absent UDS (n=190) and limited study window creating small sample size. The information gathered indicates a need for more robust urine drug screening in patients with psychotic symptoms. The increased incidence of cannabis use in psychotic patients post-legislation, while not statistically significant, warrants further research in years to come to examine the association between cannabis use and psychosis in Vermont and the safety of recreational cannabis