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.”
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.”
Hellbound and Down 