A study of a regulated cannabis sales pilot in Basel, Switzerland, has found small reductions in depression and anxiety symptoms among participants, and less problematic use in those whose use was most concerning at the start. The findings were reported by leafie.

The research, published in the journal Drug and Alcohol Dependence, analysed 374 regular cannabis users during the first year of the Weed Care project, which began in January 2023.

What the study found

Average depression and anxiety scores fell slightly over the year. Participants used cannabis on an average of 20.1 days a month after 12 months, up from 18.7. The amount they consumed on each day of use did not change significantly.

The clearest improvement in problematic use was among the higher-risk group. Their average score on a questionnaire assessing problematic cannabis use fell from 16.1 to 13.9. That is still slightly above the threshold of 13 for possible cannabis use disorder.

The researchers concluded that “these findings suggest that regulated access was not associated with deterioration in mental health or cannabis use”.

How the Basel pilot works

The pilot is one of several running in different regions of Switzerland. Under the scheme’s original plans, existing adult cannabis users could register to buy cannabis from nine pharmacies. Products were quality-controlled and labelled with their THC and CBD content, with THC levels capped at 20%.

Monthly purchases were limited to the equivalent of ten grams of THC, so the quantity available depended on potency. Pharmacists were trained to explain lower-risk consumption and to recognise signs that someone might need more help, including referral to a study doctor or a treatment service.

Other evaluations

A separate evaluation of seven pilot schemes, commissioned by the Swiss government, also reported early improvements in anxiety and depression. It suggested that removing the stress of buying on the illegal market could help explain those changes. Participants also described benefits from buying cannabis without the stigma attached to the illegal market.

In a three-year update published in March 2026, the University of Basel reported continued reductions in problematic use and improvements in mental health among Weed Care participants. The project has been extended until January 2027, and a final report is expected in 2027.

Why it matters in the UK

Cannabis remains a Class B drug under the Misuse of Drugs Act 1971 in the UK, and non-medical sales are not permitted. Evidence from overseas pilots such as Basel’s is often cited in debates about drug policy. The study followed participants who already used cannabis regularly and had no control group of non-participants, so it does not show how regulated sales would affect the wider population.