Legalizing marijuana for adult use is linked to gradual reductions in violent crime—while medical cannabis legalization is associated with lower rates of property crime—according to a new study.
As more states move to enact legalization, researchers at Jack Welch College of Business and Technology, Barnard College, National Chengchi University and Longwood University set out to investigate the relationship between different versions of the reform and crime trends.
The study, published in the journal Economic Modelling, identified a unique divide when looking at the impact of legalizing cannabis for recreational as compared to medical purposes, with analytic models revealing how different forms of regulated access seem to be associated with different patterns in criminal activity.
“Novel policies may generate unintended spillovers, particularly when legalizing one activity alters incentives for other forms of crime,” the study authors wrote. “Marijuana legalization provides a useful setting to examine such effects, given the staggered adoption of medical and recreational laws across all 50 U.S. states.”
“We find that medical legalization reduces property crime, while recreational legalization reduces violent crime.”
While initial analyses signaled that adult-use legalization might increase property crime, once state-specific time trends where incorporated into the researchers’ models with synthetic specification, “the effect becomes negative and statistically insignificant.”
“Overall, the findings indicate that estimated crime effects are highly sensitive to identification assumptions and do not provide robust evidence of an increase in property crime following legalization, underscoring the importance of careful empirical design in policy evaluation,” the study says.
Notably, the researchers found that the impact of cannabis reform on crime is gradual, with the effects manifesting “powerfully after several years.” For advocates pushing for legalization, the authors said, that means they should exercise caution in how they frame the issue, as crime rate declines don’t appear to happen overnight.
“What emerges from our multi-step analysis is a birds-eye view of legalization: medical and recreational legalization have different impacts and operate through diverse channels, with significant lag effects,” they said. “The overarching result from our main synthetic difference in differences model is that medical legalization reduces property crime, while recreational legalization reduces violent crime.”
“Such effects support the Becker hypothesis that legalization drives out crime. Building up to the synthetic difference in difference model, we discovered that there may also be important lag effects. The diverse and potentially time-varying impacts of medical and recreational legalization raise a cautionary note to policymakers: those considering legalization should wait a few years before pronouncing on the cost–benefit impact, focus on the specific type of legalization, and study closely the outcomes from similar states.”
It’s not immediately clear from the research why medical and recreational marijuana legalization would lead to diverging crime trends, but the broader impact of the reform on crime has been studied before.
Last year, for example, a study looking at Atlanta’s move to decriminalize marijuana concluded that, contrary to warnings from some critics, the policy change in fact led to a decrease in violent crime as police turned their attention to more urgent matters.
A 2024 analysis of violence between intimate partners separately found that legalizing marijuana for adult use “results in a substantial decrease in rates of intimate partner violence.”
A 2021 study, meanwhile, found that reductions of crime generally after marijuana legalization was being significantly understated because the FBI data is inconsistent and comes from voluntary participation by local agencies.
In 2020, researchers looked at how adult-use marijuana legalization in Washington and Colorado affected crime rates in neighboring states, and the resulting study determined that passage of recreational cannabis laws may have actually reduced certain major crimes in nearby jurisdictions.
The previous year, a federally funded study found that legalizing marijuana has little to no impact on rates of violent or property crime. The policy change did seem connected to a long-term decline in burglaries in one state, however.
A 2018 study from the think tank RAND said county-level data from California suggested that there was “no relationship between county laws that legally permit dispensaries and reported violent crime,” the researchers wrote. What’s more, there was a “negative and significant relationship between dispensary allowances and property crime rates,” though it’s possible that’s the product of “pre-existing trends.”
That same year, researchers at Victoria University of Wellington and Harvard University found that medical marijuana laws essentially have a null effect of crime rates, with one big exception: A nearly 20 percent reduction in violent and property crimes in California following the legalization of medical cannabis there.
