New research from Switzerland’s pioneering cannabis pilot shows a decline in problematic use—especially among polydrug users—suggesting legal access may ease mental strain.
A First-of-Its-Kind Legal Cannabis Trial
Conducted by a consortium including the University of Basel and the University Psychiatric Clinics Basel, the Weed Careproject recruited around 370 participants. Half were given legal access to cannabis through licensed pharmacies, while the rest continued sourcing cannabis illegally.
Researchers used regular self-reported questionnaires to monitor both consumption habits and psychological well-being. The findings—published in the journal Addiction—show a “slight but measurable” decline in problematic cannabis use among those with legal access. In drug policy terms, this is significant: consumption is deemed problematic when it causes health, social, or mental difficulties, even if dependency isn’t formally diagnosed.
“Legal access was particularly beneficial for people who used cannabis alongside other substances,” said Dr. Lavinia Baltes-Flückiger, lead author and deputy head of Psychiatric Services Aargau. “This subgroup saw a notable drop in problematic use.”
Mental Health Impact: No Harm, Some Relief
Importantly, the study debunks a common concern: that legalisation might worsen cannabis-related mental health issues. After six months, both groups showed no significant difference in rates of depression, anxiety or other psychiatric symptoms.
By the two-year mark, however, researchers observed a general improvement in mental well-being among participants—most of whom had by then transitioned to legal cannabis. “Legal access eases the burden on consumers,” said Professor Marc Walter, co-lead of the study.
Towards Full Legalisation
The Weed Care project is one of seven ongoing pilot schemes in Switzerland. Collectively, these experiments are shaping the country’s path toward full legalisation.
Earlier government assessments show participants increasingly favouring safer consumption methods and reporting less stigma—especially when obtaining cannabis through pharmacies.
These data may have helped sway lawmakers: in February, the Social Security and Health Committee of Switzerland’s National Council approved a draft law to legalise the commercial sale and possession of cannabis by a 14–9 vote.
If passed, Switzerland could become one of the first countries in Europe to offer a fully regulated recreational cannabis market—founded not on ideology, but science.
More Insights on Cannabis from The Cannex
This latest Swiss study joins a growing body of international research challenging outdated narratives around cannabis use. For example, a recent U.S. study found that legal marijuana may reduce workers’ compensation claims, suggesting possible health and economic benefits (read more here). Meanwhile, emerging evidence shows that cannabis could help curb alcohol cravings in heavy drinkers (details here). And for those interested in the science behind the plant, geneticist Anna Schwabe is leading groundbreaking research into how THC content varies across strains (explore her findings).
