MedicalResearch.com Interview with: Prof. Mark A. R. Kleiman PhD Affiliated Faculty, NYU Wagner; Professor of Public Policy NYU Marron Institute of Urban Management MedicalResearch.com: What is the background for this study? What are the main findings?  Response: As state after state legalizes the sale of cannabis, the question of cannabis-impaired driving is getting more attention. There is evidence that the practice has become more common, both because cannabis use - and especially heavy, frequent use - has increased and because a distressingly large fraction of cannabis users believe, falsely, that stoned driving is safe. The natural response to the problem is to treat cannabis on a par with alcohol: fairly severe criminal penalties for impaired driving, with impairment defined by a specific level of the drug in the body. The paper argues that this would be a mistake, for four independent reasons: - While cannabis makes driving riskier, it does so by about a factor of two, with no strongly observed dependency on dosage. Alcohol, by contrast, has a steep dose-effect curve. At the legal limit of 0.08% blood alcohol content by weight, the relative risk of drunk driving is at least eight; at 0.15%, which is fairly common, the relative risk has been estimated at 30-50. So there is no justification for punishing stoned driving as severely as we punish drunk driving. - The lack of evidence of a strong dose-effect relationship suggests that a legal standard based on the content of cannabinoids in blood may not be appropriate. - Even if a blood standard were valid, the lack of a breath test would make enforcing that standard nearly impossible as a practical matter. - The long and unpredictable course of cannabis metabolism means that frequent users will be at risk of failing a drug test even when they are neither subjectively intoxicated nor objectively impaired. Worse, they would have no way of judging in advance whether or not driving would be legal. The result would be a re-criminalization of cannabis use through the back door.  (more…)