Medical marijuana has proven indispensable for many people, from autistic children to veterans with PTSD. There's even a case to be made that, used as a painkiller, marijuana could help solve the country's opioid problem.
People using medical pot aren't the only ones reaping the benefits, though. A new study suggests that medical marijuana laws (now on the books in 29 states and Washington, DC) have led to a decrease in violent crime in states that border Mexico. Areas closest to the border saw the most pronounced drop overall, as well as in crimes related to drug trafficking, which suggests that legalizing the production and distribution of marijuana in the United States is hurting Mexican drug trafficking organizations.
Mexico supplies most of the illicit drugs to the US; around $6 billion worth crosses the border every year as profit for the smugglers. It's a violent industry, and one that's hard to rein in without curbing demand. (The study authors open with an anecdote about a high-tech fence in Arizona being thwarted by a marijuana-launching catapult.) It's so easy to obtain a prescription, they argue, that medical marijuana laws (MMLs) are a de facto decriminalization. They create a quasi-experimental situation where we can begin to examine whether legal weed pushes illegal weed out of the drug market.
To see how changes in state laws affected traffickers, researchers used data from Uniform Crime Reporting Program, an FBI-maintained database. They found that MMLs were linked to a 12.5 percent decrease in violent crime—homicides, aggravated assaults, and robberies—in states bordering Mexico. Using data from the FBI's Supplementary Homicide Reports, they attributed the decrease in homicides largely to a drop in drug-related killings.
The effect is most pronounced in counties closest to the border (less than 350 kilometers or about 217 miles), and diminishes as you move further inland. The study also shows evidence of "spillover effects"—when an inland state legalizes medical marijuana, the nearest border state sees a decrease in crime. That findings support the theory that the arrival of medical marijuana leads traffickers to dial back their efforts.
One open question is whether full-on marijuana legalization would lead traffickers to focus on other drugs, such as heroin. The researchers note that the market for marijuana is the largest drug market in the US, and it can be grown cheaply in Mexico: a pound that cost $75 to grow might sell for $6,000. The market for heroin is comparatively small—though it's growing, possibly due to a crackdown on prescription painkillers.
The new study underscores the fact that drug markets are, after all, markets. They're violent, but defined by rules of supply and demand; illegal, but not beyond the law of competition. High-tech fences haven't kept out drugs or deterred the violence associated with their distribution, but legal, non-violent competitors just might.