How Medical Marijuana Laws Impact Mental Health

In recent years, the legal status of marijuana has become successively less restrictive in many countries. In the U.S., access to marijuana has been facilitated in most states since the mid-1990s—whether through medical clearance or through decriminalization of recreational use. However, liberalization is still controversial. While some fear negative consequences from addiction, others highlight the potential medical benefits for people suffering from chronic pain, nausea, or convulsions. Whether the medical benefits outweigh the potentially negative consequences due to recreational abuse is still debated.

We have investigated the effects of the eased access to medical marijuana on mental health. Importantly, our analysis allows us to assess whether medical cannabis legislation in the U.S. benefits those groups for which the laws are designed, such as people with certain medical conditions and those who experience frequent pain. The policy evaluation for the overall population additionally studies if negative effects through, for example, diversions and addiction dominate medical benefits or not.

The approval of marijuana for medical use does benefit those for whom it is intended.

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The Evidence: Mental Health Benefits for Targeted Groups

We analyzed data from nearly eight million individuals, focusing on the self-reported number of days with poor mental health per month. In our study, we did not find any evidence for a negative effect of eased access to medical cannabis on mental health. We found that while the overall reduction in poor mental health days was not statistically significant for the general population, the story changes when looking at specific groups.

For individuals likely to consume marijuana for medical reasons, we found significant beneficial effects. In states that adopted medical marijuana laws, these individuals experienced an improvement in mental health, reporting fewer days per month with poor mental health. The results were especially strong for individuals who tend to suffer from chronic pain, a key condition treated with medical cannabis. The estimates suggest that this group spends 0.3 days less per month in poor mental health due to the change in the law.

The Broader Economic Implications

The findings can inform the public and the scientific discourse, which debates the trade-off between the value of marijuana as medicine and the risk of uncontrolled recreational use. Overall, our results are in line with the hypothesis that medical cannabis legislations benefit those individuals for whom they are nominally designed without systematically harming other groups.

From an economic standpoint, improved mental health could lead to higher productivity, reduced absenteeism, and lower healthcare costs, especially for the millions suffering from chronic pain. Moreover, as medical cannabis is considered a viable substitute for more addictive substances, like opioids, eased access to medical cannabis may also indirectly help curb the opioid crisis.