New research suggests that the introduction of medical marijuana has led to a sharp drop in violent crime in the US states that border Mexico.
The study, titled Is Legal Pot Crippling Mexican Drug Trafficking Organizations? The Effect of Medical Marijuana Laws on US Crime, found that states bordering Mexican that had legalised the medicinal use of the drug saw violent crime drop an average of 13 percent.
According to the Guardian, most of the cannabis used in the US originates from Mexico. Economist Evelina Gavrilova, who co-authored the study, said: "These laws allow local farmers to grow marijuana that can then be sold to dispensaries where it is sold legally.
"These growers are in direct competition with Mexican drug cartels that are smuggling the marijuana into the US. As a result, the cartels get much less business."
As a result, there is a reduction of drug-related violence, according to the researchers.
Gavrilova continued: "The cartels are in competition with one another. They compete for territory, but it's also easy to steal product from the other cartels and sell it themselves, so they fight for the product. They also have to defend their territory and ensure there are no bystanders, no witnesses to the activities of the cartel.
"Whenever there is a medical marijuana law we observe that crime at the border decreases because suddenly there is a lot less smuggling and a lot less violence associated with that."
Gavrilova, alongside researcher Floris Zoutman and Takuma Kamada, used FBI crime reports and homicide records from 1994 to 2002 - they found that the effect of the medical marijuana laws was the strongest in California, which had a 15 percent reduction. Arizona had the lowest, but still dropped by seven percent.
The researchers found that homicides related to the drug trade fell by 41 percent, whereas robbery was down by 19 percent and non-drug-related murders by 10 percent.
Gavrilova said: "When the effect on crime is so significant, it's obviously better to regulate marijuana and allow people to pay taxes on it rather than make it illegal.
"For me it's a no brainer that it should be legal and should be regulated, and the proceeds go to the Treasury."
Thirty states currently have laws which legalise marijuana in some form, according Governing.com - these vary in degree, most allow it for the limited medical use under certain circumstances, others have decriminalised possession of small amounts of the drug.