Last year, a study was published, and reported on by McClatchey, that showed that marijuana was linked to crime more often than other commonly-abused substances. For example, the study reported, eighty percent of the adult males that had been arrested in Sacramento, California had tested positive for one or more drugs, most commonly marijuana.

White House “drug czar”, Gil Kerlikowske, often cites studies like this, warning of the dangers of legalizing marijuana, even for medicinal purposes. However, Gil Kerlikowske often makes a common college freshman argument mistake in this regard: he confuses “correspondence” with “causality.”

Just because two things are commonly found together (correspondence) odes not mean that one caused the other (causality). For example, there may be a high incidence of chocolate milk consumption among school children with low test scores. But to assume that drinking chocolate milk causes low test scores would be a fallacy. Lots of school kids drink chocolate milk. It’s available at the school, their parents aren’t around, they like it, they drink it. So do lots of high-scoring kids.

The question then is whether the use of drugs, especially marijuana, leads to crime.

Enter a new study that aims to get to the bottom of the correspondence between medical marijuana legalization and any potential crime increase. The study stated its aim this way:

Debate has surrounded the legalization of marijuana for medical purposes for decades. Some have argued medical marijuana legalization (MML) poses a threat to public health and safety, perhaps also affecting crime rates. In recent years, some U.S. states have legalized marijuana for medical purposes, reigniting political and public interest in the impact of marijuana legalization on a range of outcomes.

And what did they look at to determine their answers?

Relying on U.S. state panel data, we analyzed the association between state MML and state crime rates for all Part I offenses collected by the FBI.

These findings run counter to arguments suggesting the legalization of marijuana for medical purposes poses a danger to public health in terms of exposure to violent crime and property crimes.

One revealing fact that this study pointed out was that other studies “found a relationship between marijuana use and subsequent arrest, although once the authors removed all types of drug charges from the models, the relationship was no longer significant.”

In other words, yes there were more arrests of people who use marijuana. But most of those arrests were for HAVING the marijuana, not for some other crime.

With the easing of national opinions, not just on medical marijuana, but also on recreational use, these kinds of questions will go on being debated for some time to come.

Image via Wikimedia Commons