Every time cannabis legalization or reform policies come up for debate before state or federal legislators, there is always a prohibitionist that will step in to argue that legalizing cannabis will increase crime rates. An increasing body of evidence is showing that the exact opposite may be the case, however. A new thesis paper published on the International Scholarship website has found that states with medical cannabis programs saw a reduction in the rates of murders and robberies between 1995 and 2015.

Kenna Garrison of the Haverford College Department of Economics compared medical marijuana patient registration rates in states with legal MMJ programs to crime rates in those same states. "A one percent increase in medical marijuana registration rates decreases murder and robbery rates by 0.03 percent and 0.02 percent, respectively, and has no significant effect on other types of crime," he wrote. "These results show that increasing the legal availability of marijuana through medicalization could decrease murder and robbery rates, two crimes highly associated with the illegal drug trade."

These findings match up with several other recent research studies connecting legal cannabis with crime reduction. In 2014, researchers at the University of Texas tracked crime rates over all 50 states between 1990 and 2006 and found that the 11 states that had legalized medical cannabis by that time experienced reductions in rates of homicide and assault. Even the FBI's official crime statistics support this conclusion, showing a marked decrease in violent crime in Washington following the state's recreational legalization of cannabis in 2012.

Garrison acknowledged that "previous research has analyzed the effects of the implementation of medical marijuana laws on crime rates," but notes that his study "is the first to study how the size of the medical marijuana market affects crime rates." The author found that the states with the largest populations of medical cannabis users were linked to the greatest reductions in murders and robberies. Hopefully, as the body of research continues growing, the myth of cannabis being linked to violent crimes can finally be put to rest.