Newspaper article

Sheriff Stanek's Marijuana Comments Confuse Correlation and Causation

Newspaper article

Sheriff Stanek's Marijuana Comments Confuse Correlation and Causation

Article excerpt

In a Sunday commentary in the Star Tribune and later in an interview on Minnesota Public Radio, Hennepin County Sheriff Rich Stanek made the classic mistake this week of confusing correlation with causation.

While arguing against the legalization of marijuana, Stanek noted that "approximately 54 percent of males arrested for violent crime test positive for marijuana in Hennepin County."

That observation, he stressed in both the commentary and the interview, points to "a direct connection between marijuana and violent crime."

Well, it may show a correlation between the two, but it doesn't show a causation. Just because half of the men arrested for violent crime in Hennepin County test positive for cannabis (a drug that can apparently linger in the body days or even weeks after it is used, by the way), doesn't mean that the cannabis caused their criminal activity.

It could also mean that men who commit violent crimes are, for whatever reason, more likely to smoke marijuana.

"A" may be associated with "B." But that doesn't mean "A" caused "B."

Research is inconclusive

Actually, the relationship between marijuana and violent crime is still very much up in the air, scientifically speaking. That's the clear message from a long but painstakingly thorough paper on the topic that was published in the Journal of Drug Education in 2011.

In the paper, Southern Utah University sociologist Michael Ostrowky reviews the leading theories and key research on the relationship between marijuana use and aggressive/violent behavior.

He concludes that the findings are all over the place and thus inconclusive.

"Taken together, the results of some studies suggest that marijuana use and violence are positively associated, some research has found no association, and other studies even reveal that marijuana use can reduce aggressive behavior," he writes. "These conflicting findings are not overly surprising, considering that marijuana has been classified at different times by different investigators as a depressant, a stimulant, a hallucinogen, and a narcotic."

Dueling studies

Here's a sampling of some of the conflicting studies discussed by Ostrowsky in his article, starting with those that found no significant relationship between marijuana use and violent behavior:


Utilizing longitudinal data from a community cohort of African Americans, Green, Doherty, Stuart, and Ensminger (2010) did not find an association between heavy adolescent marijuana use and violent crime.


Pedersen and Skardhamar (2010) examined data from the Young in Norway Longitudinal Study and found no evidence that use of cannabis is associated with an increased risk of subsequent non-drug- specific criminal charges, such as violence.


In a qualitative, cross-sectional study of Canadian clients attending substance abuse treatment programs, Erickson, Macdonald, and Hathaway (2009) discovered that alcohol, cocaine, and crack were the substances most implicated in the client's descriptions of their drug-related violent incidents. In fact, the authors report "it is noteworthy how seldom cannabis was mentioned."


Using cross-sectional internet survey data, Denson and Earleywine (2008) found no relationship between marijuana use and aggression once other factors were taken into account. …

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