In Switzerland, a pioneering study has begun to investigate how regulated access to cannabis affects user behavior and mental health. The Weed Care study, initiated in January 2023, is a collaboration among the Department of Health of Basel-Stadt, the University of Basel, the University Psychiatric Clinics Basel, and Psychiatric Services Aargau. This research marks Switzerland’s first randomized controlled trial comparing the effects of legal cannabis access versus illegal procurement.
The study involved approximately 370 adult cannabis users divided into two groups for the first six months. One group received legal access to cannabis products through nine local pharmacies, supplemented with optional counseling services. The control group continued to source cannabis from illegal markets. Throughout the study, participants provided data on their consumption patterns and mental health through regular questionnaires, focusing on aspects such as anxiety and depression.
Dr. Lavinia Baltes-Flückiger, a lead researcher, noted, “This is the first controlled, randomized study of its kind in Switzerland.” Findings from the initial phase, published in the journal Addiction, reveal a modest decrease in problematic cannabis use among those with legal access. Problematic use was defined as consumption linked to negative health, psychological, or social consequences, independent of clinical dependence. The most significant reductions were observed among individuals who also used other drugs, highlighting a notable shift in this subgroup.
Despite these changes in cannabis usage, no significant differences in symptoms of depression or anxiety were recorded between the two groups after the six-month period. Following this phase, the control group was granted access to legally distributed cannabis, in accordance with the pre-agreed study protocol.
An interim analysis conducted after two years indicates ongoing mental health improvements among participants who continued in the study. Researchers report reduced psychological strain among these individuals, suggesting that continued legal access to cannabis may support better mental health outcomes.
Further long-term analysis is expected to provide more detailed findings on how structured access to regulated cannabis could influence user behavior and health over time. The study’s outcomes could play a vital role in shaping future cannabis policies in Switzerland and potentially inform regulations in other regions.
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