The high road

Graphic by Joseph Valdez

Clement Dupuy is the President of Yale’s chapter of Students For Sensible Drug Policy (SSDP).

On Mar. 23, Yale Professor Deepak D’Souza made an argument that drug policy reformers have struggled to respond to for years: legalizing marijuana will lead to increased rates of drugged driving. While potentially convincing at face value, this claim drug war apologists have been making for years disintegrates upon scrutiny. It does so for two reasons. First, we don’t actually know that regulating marijuana leads to higher rates of drugged driving. And second, even if it does, there are ways of tackling this problem that don’t involve continuing America’s disastrous drug war on the poor and people of color.  

The problem with linking marijuana use to impaired driving is that THC, the active component in marijuana that makes people “high,” stays in your system long after its effects have worn off. In heavier users, metabolites can stay in the bloodstream up to thirty days past the time of last usewell after a user is no longer impaired. Thus, a test that finds THC metabolites in a driver’s blood doesn’t say anything about whether a driver was impaired at the time of a stop.

This means that the increased rates of drivers testing positive for THC in states like Colorado merely tracks increased use of marijuana by adults (which we would expect) but not necessarily increased impairment. In fact, D’Souza himself admits this in an article the Herald ran last week when he acknowledged that we need a test that can “differentiate current use (at the time of the incident or being pulled over) from remote usewe don’t yet have such a test.”

Certainly, law enforcement should develop a reliable field sobriety test to detect people whose recent marijuana use has compromised their driving abilities, but this does not mean that legalization will lead to dramatic increases in actual impaired driving. In fact, a 2015 National Highway Transportation Safety Administration report directly disproved D’Souza’s underlying assumption that marijuana impairs driving at all. Studies on marijuana and crash risk showed “reduced risk estimate or no risk associated with marijuana use” when they controlled for age.

As a side note, it should be mentioned that other claims drug war apologists make in favor of prohibition also don’t hold water. For example, D’Souza asserts: “It’s pretty clear: states that have legalized [marijuana] for recreational or medical have much higher rates of cannabis use among their youth than states that haven’t.”

This statement is patently false. Colorado, for example, saw a 12% drop in youth marijuana use in the years following legalization according to data from the National Survey on Drug Use and Health. A 2015 study in The Lancet found that the 21 states with medical marijuana show equal or lower youth use rates compared to states without it.

All that aside, let’s grant the claim that taxing and regulating marijuana for adult use does in fact increase rates of impaired driving. Does this mean we should keep it illegal? The answer is no, given how much more harmful prohibition is than responsible regulation.

According to the White House Office of National Drug Control Policy, cartels in Mexico make $6.63 billion just from marijuana sales to the U.S. Instead of going to violent criminal organizations, tax-free, this money could be sustaining jobs in the U.S. and the revenue could be funding schools like it does in Colorado. Instead, at a time when one third of murders go unsolved in the U.S., according to NPR, the U.S. spends $8.7 billion per year enforcing marijuana laws, according to Harvard Economist Jeffrey Miron. 88% of those arrests are for possession only.

And these marijuana laws are not enforced equally: despite using marijuana at the same rates as white people, Black people are four times more likely to be arrested for it. An ACLU study found that although Black people make up just 15% of people who use drugs, they account for 37% of those arrested, 59% of those convicted, and 74% of those sentenced to prison for nonviolent drug offenses.

Professor D’Souza’s argument may have some weight to it, depending on what the data from other states show. It is not unreasonable to think that once marijuana becomes more accessible, more people will use it. Certainly, some of those people will use it irresponsibly and threaten public safety by driving under the influence. But there are ways to address this problem that don’t involve disproportionately arresting people of color and branding them with a criminal record that will prevent them from obtaining employment, housing, and even financial aid for education for the rest of their lives. Presumably, rates of drunk driving rose after the repeal of Prohibition in the 1930s, but does anyone really want to return to the days of Al Capone? Probably not.  

To minimize the risk of impaired driving, the U.S. should divert some of the tax revenue it will receive from taxing and regulating marijuana to education, prevention, and treatment. It could fund campaigns against impaired driving – just as it does with drunk driving. Certainly, this world is better than the one in which 100,000 people have died at the hands of senseless violence in Mexico because we keep funding the cartels that inflict it.

2 Responses

  1. Mr. Dupuy is correct in all the evidence he cites. The latest data that was presented at the Cannabis Research Workshop at Washington State University I just attended show youth rates of cannabis use have declined in Washington, Oregon and Colorado since adult use of cannabis was legalized. Also, THC levels in the body do not predict impairment.
    What Mr. Dupuy is unaware of is that there is now an app in the App Store that actually measures impairment from marijuana, alcohol or other sources. It is called DRUID (an acronym for “DRiving Under the Influence of Drugs”. DRUID measures reaction time, hand-eye coordination, balance, time estimation, and decision making and integrates all the measures into an overall impairment score. DRUID demonstrates that measuring marijuana impairment is available now.  The app permits individuals to assess their own level of impairment (or that of the designated driver) and determine whether they are impaired.  See more at

    DRUID was recently featured on All Things Considered:

    and on television:

    After getting my Ph.D. at Harvard, I have been a professor in the Psychology Department at UMass/Boston for 40 years, with a specialty in research methods, measurement and statistics.

    Michael Milburn, Professor
    Psychology Department

  2. Joe Gordon says:

    Legalization has led to lower us of marijuana because the economic effect of less recruitment of new customers that occurs when the black market can make huge profits. The government is subsidizing the spread of drugs, and should treat all addicts like they have a disease like alcoholism. Did we learn nothing from prohibition? Where has all the tobacco lawsuit money gone? Maybe that should be used to show the possible loss of ambition and other side effects of drugs.

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