Medical Cannabis Laws Show Limited Population-Wide Mental-Health Effects, With Possible Benefits for Patients in Pain

A 2024 study found that medical cannabis laws were associated with better self-reported mental health among people who appeared most likely to use cannabis for medical purposes—particularly those likely to experience frequent pain. The researchers did not, however, find a statistically significant improvement across the U.S. adult population as a whole.

The study, “Medical marijuana laws and mental health in the United States”, was published online by Health Economics, Policy and Law on April 2, 2024. Jörg Kalbfuss, Reto Odermatt and Alois Stutzer examined whether the introduction and expansion of medical marijuana laws across U.S. states were followed by changes in residents’ mental health.

The researchers analyzed approximately 7.9 million usable responses from the Behavioral Risk Factor Surveillance System collected between 1993 and 2018. Respondents reported how many days during the previous 30 days their mental health—including stress, depression and emotional problems—had not been good.

Because the main survey did not consistently ask respondents why they used cannabis, the researchers used data from the National Survey on Drug Use and Health to estimate individuals’ likelihood of using marijuana recreationally, using it for medical reasons or experiencing frequent pain. These were statistical propensities, not confirmed diagnoses or direct classifications of each participant’s cannabis use.

Benefits appeared concentrated among likely medical users

At the population level, states that adopted medical marijuana laws showed a small decline in reported poor-mental-health days, but the overall estimate was not statistically significant. In other words, the study did not establish a measurable improvement in mental health for the general adult population.

The results differed among population groups. The researchers found no statistically significant changes among people with a high propensity for recreational cannabis use or among likely abstainers. By contrast, people who appeared more likely to use cannabis for medical purposes reported fewer days of poor mental health after access was liberalized. Participants considered likely to experience frequent pain showed a similar pattern, with an estimated reduction of roughly four poor-mental-health days per year.

The findings are consistent with the possibility that improved access helped some patients manage pain or other health problems, which in turn may have improved their well-being. They do not show that cannabis treats depression or other mental-health conditions, nor do they demonstrate that medical cannabis laws caused the reported changes for every individual.

The study used changes in state policy over time, along with demographic and policy controls, rather than assigning patients to receive cannabis in a clinical trial. Its conclusions therefore concern associations between legal access and self-reported mental health. The authors also cautioned that results from earlier medical-marijuana programs may not automatically apply to newer or broader forms of legalization.

Switzerland is conducting a separate set of policy experiments

The University of Basel study is based on U.S. data and should not be confused with Switzerland’s cannabis pilot projects. One of those projects, Züri Can – Cannabis with Responsibility, is led by the University of Zurich with support from the city. It examines whether regulated access, product information and counseling can promote lower-risk cannabis use.

Züri Can began offering study cannabis through controlled outlets in August 2023. Participants can obtain products from pharmacies, cannabis social clubs or the city’s drug-information center, allowing researchers to compare different models of regulated access. The project is designed for up to 3,000 adult residents of Zurich and has been extended through October 2028.

According to the project’s status page, 2,472 people had been enrolled and authorized to purchase study cannabis as of August 12, 2026. The participants are predominantly men, and people aged 28 to 32 represent the largest age group. The project’s sales data and health assessments are intended to inform future Swiss cannabis policy; they are not evidence that the U.S. medical-marijuana findings apply directly to Switzerland.

Taken together, the research suggests a cautious conclusion: medical cannabis laws may improve self-reported mental health for some people who use cannabis for medical reasons, especially those dealing with frequent pain, while producing no clear population-wide mental-health benefit. More research—including long-term and clinical studies—is needed to determine which patients benefit, which risks may accompany treatment, and how regulation affects outcomes over time.