Mental health in people with hazardous cannabis and alcohol use - insights from a study of regulated cannabis sales

Background and aims: Although cannabis is illegal for recreational purposes in most countries, recently a growing number of legislators have initiated its decriminalization in numerous ways. In Switzerland, the Züri Can study is among multiple pilot projects evaluating regulatory frameworks for legal cannabis sales.  
The aim of this observational study is to assess the impact of regulated cannabis sales within a framework promoting lower-risk cannabis use on consumption behavior, as well as mental and physical health of study participants. 

Methods: In the Züri Can study, a total of 2100 adult cannabis users can legally purchase cannabis at a pharmacy, cannabis social club, or the municipal drug information center over a period of three years. A distinctive feature of the study is a multi-stage screening process in which trained staff at the points of sale check the presence of inclusion and exclusion criteria. If medical contraindications are suspected, a detailed assessment is carried out by the study physicians.  
Participants’ mental and physical health is evaluated every six months through well-established questionnaires assessing symptoms of depression, anxiety, psychosis, and insomnia among other parameters. Hazardous use of alcohol and cannabis is assessed via AUDIT-C and CUDIT-R scores.  

Results: In this short presentation, we will describe the study population baseline demographics, e.g., participants’ age, gender, educational attainment, and socioeconomic status. We will also present early findings from surveys conducted in the first six months regarding the mental health of study participants, including measures of depression, anxiety, and the use of other psychoactive substances. An evaluation of data from 2023 demonstrates a comparatively low level of mental illness burden regarding depression, anxiety, and sleep disorders. Simultaneously, more than half of the study participants report hazardous alcohol consumption (AUDIT-C >2 for women, >3 for men) and hazardous cannabis use (CUDIT-R > 7); figures significantly higher than those found in the general population.

Discussion: Preliminary data indicate that Züri Can participants on average display good mental health. This is particularly striking given that more than half of participants show hazardous use of cannabis and alcohol. This apparent discrepancy could be due to the multi-stage assessment of the inclusion and exclusion criteria, in which appropriately trained staff of the points of sale were included. The fact that there is a low burden of mental illness despite hazardous alcohol and cannabis use offers opportunities for interventions that specifically target problematic substance use in a usually hard-to-reach population.