More on Driving under the influence of Marijuana

There was a fascinating article published on the issue of driving under the influence of marijuana this past Monday in the New York Times.

Marijuana and driving is an issue of increasing relevance as US states continue to legalize medical marijuana and Colorado and Washington State have now legalized recreational marijuana.  The challenges associated with setting a specific standard for driving under the influence of marijuana have already been discussed on this blog but in a nutshell there is one major challenge. That challenge is that similar blood levels of THC can mean very different things for various people and represent very different levels of driving impairment.  Chronic users can have relatively high levels of THC regularly in their blood that correspond to much lower deficits in driving performance compared to novice users.  It also doesn’t help that marijuana blood levels currently have to be tested for with a blood or urine samples compared to a Breathalyzer test for alcohol.

The interesting position emphasized in the article and put forth by Eduardo Romano at PIRE and Mark Klein at UCLA is that alcohol is so much more dangerous than marijuana when it comes to driving under the influence that efforts to change DUI policy should focus on alcohol as opposed to marijuana and on lowering the current alcohol BAC levels from 0.08 to 0.05.  A recent paper published by Romano in the Journal of Studies on Alcohol and Drugs did not find a statistically significant increased risk of a fatal crash associated with marijuana when controlling for demographics and alcohol.  Other research suggests that any measurable THC is associated with a doubling of crash risk.  Compare this to alcohol though where the crash risk increases nine fold at the 0.08 level for adults (it is even higher for those under 21).

The data does seem to indicate that driving while under and influence of alcohol is more dangerous compared to driving under the influence of marijuana but the policy environment seems receptive to taking action on marijuana and driving while the recent recommendation by the National Transportation Safety Board to move alcohol BAC levels from their current level of 0.08 to 0.05 doesn’t seem to have much traction (at least yet).

Given the current receptivity to address marijuana related issues I think it make sense to take advantage of it by doing the relevant research and then making informed policy decisions.  This does not take away from the importance of moving alcohol BAC levels in the US from 0.08 to 0.05 but the current window of opportunity seems to be marijuana specific and it is not clear to me that advancing marijuana related DUI policies detracts from efforts to advance alcohol DUI policies.

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