Allowing legal access to cannabis can reduce instances of Cannabis Use Disorder (CUD), a Swiss study has shown.
The research, published in the peer-reviewed journal Addiction, is the first-ever randomised controlled trial comparing legal cannabis access to illegal cannabis access.
The six-month trial, which began in August 2022, involved 374 participants randomly assigned to two groups: half obtained cannabis legally through the regulated Weed Care programme, while the other half continued to source from the illegal market. The research will continue until summer 2025, but these initial findings after six months show significant results. Researchers specifically wanted to explore if there was a difference in instances of Cannabis Use Disorder (CUD), and how cannabis affected depression, anxiety, and psychotic symptoms, cannabis consumption amount, alcohol, and drug use.
“There has never been a controlled, randomized study like this before,” said lead author Dr. Lavinia Baltes-Flückiger. “Previous results were based on purely observational studies.”
Participants in both groups were monitored through questionnaires that probed them on details of their cannabis consumption and their mental health.
The study found that participants with legal cannabis access experienced a reduction in CUD symptoms compared to those using illegal cannabis. This effect was particularly pronounced among users who also used other drugs, suggesting that regulated cannabis markets may provide additional protection for more vulnerable users. No significant differences were observed between the two groups in mental health outcomes or the amount of cannabis they consumed, indicating that legalisation did not lead to increased use or adverse effects.
“Our results showed no evidence that public health-oriented RCL [recreational cannabis laws] increased the severity of self-reported cannabis misuse and related mental health outcomes at 6 months compared to the illegal market. Instead, there was some evidence that cannabis misuse was reduced,” the study said.
Researchers acknowledged the study had limitations. These included the exclusion of potential participants with acute psychosis, suicidal ideation and severe cognitive impairment, and the accuracy of self-reported data.
The study authors asserted that legal cannabis laws were not observed to lead to a rise in cannabis related harms or increased use, and that cannabis users who use other drugs were seen to experience increased levels of protection from instances of CUD than those who used illegal cannabis.
“In this randomized controlled study, a public health-oriented RCL did not lead to an increase in cannabis use and cannabis related harms, while cannabis users with other drug use could benefit in terms of a significant reduction in self-reported cannabis misuse,” the study said.
”Our results indicate that public health-oriented RCL could be an effective policy model to make cannabis safer without increasing cannabis use and cannabis-related harms. These results contribute to an evidence-based cannabis policy and inform policymakers, clinicians and the public.”
These findings provide valuable evidence for policymakers considering cannabis regulation models. After the initial six-month period, participants who had been in the illegal cannabis group were offered the opportunity to join the main Weed Care study, allowing them to access legal cannabis until the research concludes this summer.
