The evidence presented in this brief suggests that legalization of marijuana for medical or recreational use results in:
1. Patients substituting marijuana for other drugs, including opiates.
2. Marijuana consumers substituting legitimate marijuana for illicit marijuana.
3. A significant reduction in crimes associated with marijuana production, distribution, sale and possession.
4. Reductions in other crimes, including some property and violent crimes.
These effects vary by location, with reductions in property and violent crimes being most pronounced in locations close to the Mexican border due to the diminution of activities of Mexican drug trafficking organizations and affiliated gangs. Medical marijuana legalization also appears to be associated with a reduction in drunk driving.
The effects of the legalization of marijuana for recreational use are less clear. In addition, there is evidence that depenalization of possession increases the demand for marijuana. In states that have not also legalized marijuana either for medical or recreational use, this may lead to increases in crime (though the evidence is weak). However, in states that have legalized marijuana for either medical or recreational use, any adverse effects of such increased demand are more than offset by reductions in crime associated with legalization.
The largest benefits in terms of crime reduction, with the possible exception of traffic-related crimes, come from the legalization of marijuana for adult recreational use. Moreover, given the strong relationship between the reduced price of marijuana and reduced criminal activity associated with marijuana production, distribution and supply, these benefits are likely to be stronger in markets that are more competitive.