An argument against the legalization of the cannabis market is that such a policy would increase crime. Exploiting the recent staggered legalization enacted by the states of Washington (end of 2012) and Oregon (end of 2014) we show, combining difference-in-differences and spatial regression discontinuity designs, that recreational cannabis caused a significant reduction of rapes and thefts on the Washington side of the border in 2013-2014 relative to the Oregon side and relative to the pre-legalization years 2010-2012.
The presumption that drugs and crime are causally related is a major argument in support of a prohibitionist approach to substance use. Three possible reasons have been suggested for
why illicit drug use may increase crime (Goldstein, 1985): psychopharmacological effects (the“reefer madness”), stealing to buy expensive drugs, and drug wars within the system of drug distribution. Such concerns are at center stage in the current debate about whether restrictions to cannabis sale and use should be relaxed or not. The legalization and liberalization of the cannabis market may shut down the drug wars channel and reduce prices, but it may exacerbate the psychopharmacological channel. According to the California Police Chiefs Association(2009), “public officials and criminal justice organizations who oppose medical marijuana laws often cite the prospect of increased crime”. Supporting this presumption, case studies of crime reports found drugs to be a contributing factor (Goldstein, 1985), and it has been observed that a higher percentage of persons arrested test positive for illicit drugs compared with the general population (US Department of Justice). Yet, research on the recent wave of legalization of cannabis for medical use (“medical marijuana laws”, MML henceforth) in the US yields mixed results on the association between illicit drug use and crime. Some researchers find no significant relationship between MML and crime (Keppler and Freisthler, 2012; Braakman and Jones, 2014; Morris et al., 2014; Freisthler et al., 2016; Shepard and Blackley, 2016), while others show that MML may reduce some kind of non-drug crimes either because of reduced activity by drug-trafficking organizations (Gavrilova et al., 2014) or because the police reallocates effort away from drug-related crimes and towards other types of offenses (Adda et al., 2014).