In Switzerland, legal access to cannabis reduces problem use

A Swiss study reveals that’legal access to cannabis can reduce problem drug use, particularly among people who also use other substances. This is the very first randomized controlled trial in Europe to directly compare the effects of’regulated access to cannabis with those of the illegal market.

The Weed Care pilot program, launched at Basel early 2023, is part of a wider initiative to inform evidence-based cannabis policy in Switzerland. The project is a collaboration between’University of Basel, the Aargau psychiatric services, the Basel University Psychiatric Clinics and the Basel-Stadt Department of Health.

Controlled study shows reduction in cannabis use disorders

Published in the scientific journal Addiction, the study followed 374 adult participants for six months. Half of them were allowed to buy regulated cannabis The other half continued to obtain cannabis illegally. Participants reported on their consumption habits and mental health using regular questionnaires.

According to the Dr Lavinia Baltes-Flückiger, study co-director and lead author, this study marks a milestone in cannabis research: «There has never been a randomized controlled study like this before.»

The results revealed a significant drop in problematic cannabis use, officially known as cannabis use disorder (CUD), in the group with legal access. This trend was particularly pronounced in people who were also taking other drugs, suggesting that a regulated cannabis market could offer additional protection for high-risk consumers.

No increase in drug use or mental health problems

One of the main conclusions of the study is that legalization does not lead to an increase in consumption or deterioration in mental health. Despite concerns that legal access might encourage higher consumption or trigger psychiatric symptoms, the study found no no significant difference between the two groups in terms of levels of depression, anxiety or psychotic symptoms.

These results are consistent with previous observational studies, but provide more solid proof thanks to the randomized controlled design.

«Legal access eases the burden on consumers,» said the Professor Marc Walter University of Basel and Aargau Psychiatric Services.

At the end of six months, the control group was also offered a legal access to cannabis for the remainder of the study, scheduled to end in summer 2025. An interim evaluation carried out after two years revealed a overall improvement in mental well-being among the remaining 300 or so participants.

«Our results indicate that recreational cannabis laws focused on public health could be an effective policy model for making cannabis safer without increasing its use or related harm,» the researchers concluded.

Wider implications for cannabis policy in Europe

The Weed Care program is just one of seven pilot trials on recreational cannabis currently underway in Switzerland. Preliminary data from these trials, published by the Swiss government, show a positive trend in the development of the drug. towards safer consumption methods and a de-stigmatizing effect for consumers who access cannabis through regulated channels.

In February 2025, Swiss politicians have approved a project to regulate the recreational cannabis market for adults. The proposed federal law would allow citizens to legal cultivation, purchase, possession and consumption of cannabis. The Social Security and Public Health Committee adopted the project by a majority of 14 votes to 9.