Please do not support the proposed THC/DUI Bill
Open Letter to Legislators on the THC/DUI bill:
I am a social scientist and PhD candidate at the University of Colorado at Boulder, where I have been engaged in research on cannabis for several years. In 2012, Colorado passed Amendment 64 to “regulate marijuana like alcohol.” Since marijuana regulation is new, it makes sense to base regulations for cannabis on those for alcohol, but it is important to remember that this does not make marijuana actually “like” alcohol” in its scientific properties. Cannabis does not work like alcohol, and for this reason, the THC/DUI bill is misguided in trying to set laws as if they are the same.
To justify passing the THC/DUI bill, three solid pieces of evidence are required. First, we should know levels that indicate intoxication. Second, there should be an accepted and reliable way to accurately measure that level of intoxication. Third: there should be proof of sufficient need to encroach on individual rights based on danger to the public. Please allow me to address these in turn.
1. Knowing levels that indicate intoxication. Marijuana is not “like alcohol” in terms determining impairment. The science is simply not there. A nanogram limit cannot yet be clearly and unambiguously linked to impairment. Based on the best evidence currently available (Grotenhermen and colleagues review of the literature in 2005, the Medical Marijuana Industry Group report in 2011, which responded to the first proposal of this law, and William Logan’s 2012 chapter reviewing the literature on marijuana and driving in Mahmoud ElSohly’s book Marijuana and the Cannabinoids), it is clear that we simply don’t know the correct limit over which drivers are impaired. It turns out that inexperienced or occasional cannabis consumers may be subjectively impaired at a much lower nanogram level than medical or social cannabis consumers with years or decades of experience. Logan (2012) summarizes the evidence we have to-date and is clear on the point: it is not possible to use blood tests of THC to distinguish between recent impairment and “more distant higher-intensity marijuana use” (286). For medical consumers or other chronic consumers of marijuana, heightened THC in the blood may last long after the subjective experience of impairment. In fact, maintaining higher levels of cannabinoids in one’s system may be related to medical benefit for those treating severe pain and serious illness.
2. There should be an accepted and reliable form of measurement that indicates intoxication. On the second point, it is crucial to acknowledge that marijuana and alcohol are not the same when it comes to how the body processes them. These two substances are metabolized in completely different ways by the body. Alcohol is water soluble. It is rapidly and evenly distributed throughout the body, and for this reason, breath tests can be used to approximate blood alcohol level, and both tests can be reliably used to indicate impairment. There is no such proxy for cannabis. it’s distribution in the body is based on the unique pharmacokinetics of THC, its distribution in the body and the way it is metabolized. Marijuana is lipophilic, it dissolved in fat, not water, and is metabolized quite differently than alcohol. We do not have reliable estimates that are consistent across different individuals, allowing us to measure levels of impairment with the same assessments we use for alcohol. In fact, breath tests cannot be used to measure cannabis for this reason. Instead, blood samples, the most intrusive type of test, would be necessary. Because blood tests are highly intrusive, clear and unambiguous evidence for such an intrusion on individual rights is warranted.
3. Finally, we should be able to link the use of the substance to a clear public health danger on the roads. Cannabis has not proven to present a similar level of risk in traffic accidents. On this final point, we have to ask, is a separate law warranted when marijuana intoxication is already included under existing DUI-D laws? The answer: no. There simply is not data that suggests cannabis alone greatly increases accidents or risks on the road at a level that warrants a new, separate DUI law specific to cannabis. In the case of alcohol, there are clear and well established relationships showing increased risk of accidents linked with blood alcohol levels. Less data exists for cell phone use and prescription drug use, but those studies have consistently shown significant risk ratios that indicate significant crash risks. The data on marijuana shows lower risks than these other factors. The exception is when marijuana use and alcohol use are combined. Again, Logan’s review of the data on relative crash risk following marijuana use, “studies that made odds ratio assessments based on the presence of the inactive THC-COOH metabolite uniformly failed to show significant differences at the p=0.05 level in rate of accident involvement for the drug-positive drivers” (287). Recent evidence suggests that accident rates decrease in states with regulated medical marijuana. This has been attributed to the reduction of alcohol use in favor of marijuana, resulting in fewer alcohol-impaired drivers on the road, discussed by Time magazine in an article by Maia Szalaviz from December 2011.
For these reasons, those who have studied the issue and reviewed all available evidence do not recommend the use of per se limits without better science. To the degree that such policies are used, they urge great caution, and suggest that other methods for assessing impairment not be discarded or demoted given the lack of credibility on the currently available objective measures.
The current bill under consideration belongs to a dying breed. “Get Tough” policies have been popular among politicians because they have equated with success in the polls, but as more and more people acknowledge that the War on Drugs approach to drug control is a failure, these nonscientific approaches are bound to lose traction with the voting public.
Clearly no one wants impaired drivers on the road, and no one is arguing for that. This THC/DUI bill will do little to help prevent that, and it may end up punishing people who are not impaired. Until objective limits for cannabis intoxication can be clearly determined, measured, and linked to a genuine risk to public health on the roads, we should stick with our existing DUI-D law that already covers drug impairment.
Shelli Newhart Walker