Basel, Switzerland, is known around the world for being a center of art and culture. Additionally, as of late January 2023, it also became known as the first European city to launch a regional adult-use cannabis commerce pilot trial in which registered participants can make legal cannabis purchases from authorized pharmacies.

“This study aims to investigate the health effects of regulated cannabis sales compared to the current situation where cannabis is illegally available. Specifically, it examines whether the option of regulated cannabis sales in Basel-Stadt pharmacies is utilized and how this affects the consumption patterns and health of the study participants.” the Weed Care study’s website states about the aim of the pilot trial (translated from German to English).

“The study, conducted by the Department of Health of Basel-Stadt, the University Psychiatric Clinics (UPK) Basel, the Psychiatric Services Aargau (PDAG) and the University of Basel, investigates how a regulated sale of cannabis through pharmacies compares to the current situation, i.e. the illegal acquisition of cannabis, on the consumption behavior and health of the study participants.” the University of Basel writes about the Weed Care study.

“A key argument in favor of controlled dispensing in pharmacies is that certain quality requirements are placed on the production and processing. The study cannabis is free of pesticides, impurities and synthetic cannabinoids and has been approved by the FOPH for this study. In addition, the active ingredient content is declared.” the University adds.

After more than three years of the regional adult-use cannabis commerce pilot trial operating in Basel, authorities continue to find positive results.

“Thanks to the Weed Care pilot project, the inhalation of smoke from joints containing tobacco has fallen significantly, the cantonal health department said on Thursday. Health risks have been reduced and consumption has not increased.” stated Swiss Info in its local coverage. “The introduction last autumn of non-smoked cannabis products – namely vaporisers and oils – into the controlled sales scheme has been a success: they now account for nearly a fifth of consumption, without total consumption having increased, the health department added.”

An interdisciplinary research team affiliated with the Addiction Department of the Department of Health of the Canton of Basel-Stadt, the University of Basel, the University Psychiatric Clinics Basel (UPK), and Psychiatric Services Aargau previously published findings in May 2025 from a study that relied on data from the Weed Care pilot trial. The study’s findings, which were the first academic reporting of its kind, were published on the University of Basel’s website in addition to being published in the academic journal Addiction.

“We measured the effects of public health-oriented cannabis access compared with the illegal market on cannabis use and related mental health outcomes in adult cannabis users.” the researchers stated about their 2025 study. “This was a two-arm, parallel group, open-label, randomized controlled trial. Follow-up outcome measurement took place after 6 months.”

“The primary outcome was self-reported severity of cannabis misuse after 6 months, as measured by the Cannabis Use Disorders Identification Test – Revised (range 0–32). Secondary outcomes involved depressive, anxiety, and psychotic symptoms, cannabis consumption amount, alcohol, and drug use.” the researchers wrote regarding their investigation’s measurements. “Public health-oriented recreational cannabis access may decrease cannabis use and cannabis-related harms, especially among those using other drugs.”

A common talking point among cannabis opponents is that legal access to adult-use cannabis products will increase problematic cannabis use in society. The study’s findings contradict that claim. Another common talking point among opponents is the claim that legal cannabis use will lead to a decline in mental health among consumers. This 2025 Swiss study also provided findings that addressed that claim.

“Furthermore, the study was able to dispel fears that legalization could exacerbate the psychopathological symptoms associated with cannabis consumption in addition to consumption itself: after the first six months, there was no difference between the two study groups in terms of depression, anxiety or other symptoms.” stated the University of Basel on its website at the time. “The interim assessment after two years of study shows a significant improvement in the mental state of the approximately 300 or so participants who are still taking part.”

“There has never been a controlled, randomized study like this before,” emphasized Dr. Lavinia Baltes-Flückiger, deputy head of the study at the Psychiatric Services Aargau and lead author of the study, according to the University of Basel’s reporting.