Does Marijuana Cause People to Be Violent?

A county sheriff in Minnesota went on the record claiming that there is a clear correlation between violent acts and marijuana.  He backs up his statement by arguing that 54% of those individuals books into his jail are under the influence of marijuana.  He states that around 40,000 people a year are booked into his jail and more than half of that are under the influence of marijuana.  That seems like a staggering statistic, but if you read through the lines his claim is misleading or at least vague and ambiguous.

First, the good sheriff makes a classic logical fallacy: correlation equals causation.  The mere fact that 1/2 of his bookings are those “under the influence” of marijuana does not mean that marijuana causes violent behavior.

Second, the sheriff leaves many questions unanswered in his statement.  Specifically, what does he mean “under the influence.”  Marijuana’s detectable component, THC, remains in the human body for around 30 days.  When people are booked into the Hennepin County jail they are likely subjected to a urine analysis.  This is common booking practice for jails throughout country.  If that is the case with the sheriff’s jail, then the UA will show THC in the system for the past 30 days.  Thus, if someone committed a violent act that night and was booked into jail, the sheriff may be claiming that the individual is under the influence of marijuana simply because it showed up in a UA.  That does not prove, however, that a person is under the influence at the time the violent crime was committed.  Thus, the sheriff’s statement is easily refuted.

Finally, the sheriff needs some scientific peer reviewed research before he could make such a blanketed statement.  In fact, in a brief internet search for scholarly articles on marijuana use and violence, the studies most often find a correlation between the underground economy of marijuana and violence when drug deals go awry.  Cannibis physiologically reduces aggression. It chills people out.

The sheriff may have his own personal biases against marijuana, but his attempt to link marijuana as a causing factor of violence falls far short from persuasive evidence.

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