The legalization of marijuana – both medical and recreational – has created a conundrum for states and law enforcement agencies when it comes to driving. While most states criminalize driving under the influence of marijuana, it’s been much harder for law enforcement to determine who exactly is driving under the influence – and how impaired they are.
Many states have merely decided on limits of THC metabolites that can legally be present in your bloodstream while driving. The problem with this approach, though, is that those metabolites can remain in your bloodstream long after the high has worn off.
Because of this, some states (like Colorado) require additional evidence that a person is too stoned to drive (like erratic driving, disregarding traffic lights or signs, or appearing stoned).
But the issue of driving under the influence of cannabis has been attracting a bit of attention lately in the scientific world. With the proliferation of (legal) medical marijuana, scientists want to hone in more precisely on what level of impairment a cancer patient (for example) might expect if they are using prescribed marijuana for symptom relief.
In the words of a recent Australian study: “The positioning of cannabis as a legitimate medical product produces some tensions with other regulatory frameworks…the so-called ‘zero-tolerance’ drug driving legal frameworks, which criminalize the presence of THC in a driver’s bodily fluids irrespective of impairment.”
Two new studies focus on different aspects of the question of driving under the influence of cannabis
These researchers were particularly concerned with the inequity of criminalizing the use of one medication and not another, so they compared the risks of driving under the influence of cannabis with prescription medicines “such as antidepressants, opioids, and benzodiazepines.” According to the research data, drivers taking those prescription medicines were more than twice as likely to be involved in a traffic accident as a sober driver.
Drivers who were driving under the influence of cannabis, on the other hand, were 1-1.4 times as likely to be in an accident as a sober driver. That’s not a great statistic and does highlight that driving while high is not a safe activity.
But those numbers certainly raise the question of why a person under the influence of opioids is treated differently than someone using cannabis.
The authors of the study conclude that a system that treats cannabis as a substance with no medical benefit harms patients “including criminal sanctions when not impaired and using the drug as directed by their doctor, or the forfeiting of car use and related mobility.”
Another recent study out of the University of Iowa took a different approach. For this investigation, ten drivers performed basic driving tasks on a simulator two hours after “cannabis inhalation.”
Drivers were first asked to rate their own level of impairment before being put on the driving simulator. After evaluating participants’ performance, researchers determined that drivers’ subjective experience of cannabis greatly determined how they drove:
“Thus, driver’s perceptions may result in changes to driving behavior that could mitigate the effect of cannabis…Our results provide a better understanding of how different strains of cannabis, which produce different subjective experiences for users, could impact driving safety. Specifically, we found drug effects that produce more stimulation results in less impact on driving, while those that produce a more stoned or high feeling results in a greater negative effect on driving.”
This evidence further complicates the issue of regulating driving under the influence of cannabis.
Any article on cannabis research ends with the inevitable statement that “more research is necessary.” In this case, it will be forthcoming. Another Australian study has received funding to look at the effects of medical cannabis on driving ability.
“We are grateful for this grant, and especially for the opportunity to further our research in this space,’ says lead researcher Professor Downey. ‘It is critical to quantify the potential risk these road users take when they get behind the wheel and develop methods to protect these vulnerable patients, as well as all road users.”