The Cannabis Effect on Crime: Time-Series Analysis of Crime in Colorado and Washington State

Cannabis Effect on Crime

Cannabis Effect on Crime

The Cannabis Effect on Crime: Time-Series Analysis of Crime in Colorado and Washington State.


Previous studies based on relatively weak analytical designs lacking contextualization and appropriate comparisons have reported that the legalization of marijuana has either increased or decreased crime. Recognizing the importance for public policy making of more robust research designs in this area during a period of continuing reform of state marijuana laws, this study uses a quasi-experimental, multi-group interrupted time-series design to determine if, and how, UCR crime rates in Colorado and Washington, the first two states to legalize marijuana, were influenced by it. Our results suggest that marijuana legalization and sales have had minimal to no effect on major crimes in Colorado or Washington. We observed no statistically significant long-term effects of recreational cannabis laws or the initiation of retail sales on violent or property crime rates in these states.


In many ways the legalization of cannabis by ten states and the District of Columbia, as of March 2019, constitutes a grand ongoing experiment into how a major public policy initiative does or does not accomplish its expected outcomes. One of the principal expectations of the proponents of Initiative 502, the voter-initiated bill authorizing the recreational sale of marijuana in Washington, was that crime would decrease. Crimes generally were expected to decline in number, but particularly those crimes associated with the use of marijuana (e.g., possession, black market production, sales and distribution of cannabis, burglaries or thefts believed to be committed to secure funds to purchase marijuana). Some preliminary studies released shortly after legalization have intimated that crime rates have been going up rather dramatically in some of the states that have legalized recreational marijuana (Smart Approaches to Marijuana, 2018). In Washington State, early reports suggested that the number of marijuana-related offenses such as assault, theft, harassment, and vehicular offenses increased in Washington after the legalization (Northwest High Intensity Drug Trafficking Area [NHIDTA], 2016), but that “violent crime is down since Washington legalized marijuana” (Santos, 2017). Or, paradoxically, the article by Malcolm Gladwell in The New Yorker, claiming (based on a book by Berenson, [2019]) that violent crime had increased in Washington state post legalization.