Another sheriff, another unfounded comment about marijuana and crime.

Rich Stanek, sheriff of Hennepin County, Minnesota, was quoted on Sept. 15 saying there’s “a direct connection between marijuana and violent crime.” The comments were part of an op-ed he wrote for the Star Tribune.

Stanek based his claim on the supposed fact that about 54 percent of men arrested for violent crime in Hennepin County test positive for marijuana.

Effect of The Sheriff’s Claimmarijuana-close-up

The sheriff’s view matters because Minnesota is one of several states considering medical marijuana legislation. And although that legislation is likely to pass the Democrat-controlled Legislature, Gov. Mark Dayton, also a Democrat, has said he won’t sign it unless it has the support of law enforcement groups.

With attitudes like Stanek’s, that’s not likely. Unfortunately, as the Minnesota Post pointed out in an article Sept. 20, the sheriff doesn’t seem to understand the difference between correlation and causation. The fact that most men arrested for violent crime test positive for pot doesn’t mean the pot made them violent.

Why His Conclusion Isn’t Valid

For one thing, marijuana has a long half-life, and metabolites stay in the system days or even weeks after use. So many of those who test positive probably aren’t even high at the time of the violent crime.

For another, the causation could be reversed: It could be that violent men are more likely to use weed, not that men who use weed are more likely to be violent. Or it’s possible that in some cases both the violence and the marijuana use have a separate, shared cause, such as mental illness.

In other words, just because “A” and “B” occur together more often than not doesn’t mean “A” causes “B.” “B” may cause “A,” or there may be a third factor, “C,” that causes both “A” and “B.” To put it simply, correlation is not the same as causation.


This is especially true with cannabis, where the black market is a complicating factor in every consideration. Would men who use pot be as likely to commit violent crimes if pot were legal and there were no gangs, cartels or black market? Stanek didn’t address that question.

An Invalid Statement

Instead, he insisted that weed makes men violent. In reality, there’s very little research to back that claim. According to a paper published by Southern Utah University sociologist Michale Ostrowky in 2011, there’s no consensus on the available data.

Ostrowsky’s paper, which reviewed all major research on the link between marijuana and aggression, concluded that the studies are contradictory and 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 wrote. “These conflicting findings are not overly surprising, considering that marijuana has been classified at different times by different investigators as a depressant, a stiumulant, a hallucinogen, and a narcotic.”


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