Experts are calling for research into understanding the relationship between marijuana and impairment levels, pointing out that marijuana poses a less understood risk than alcohol. The US Transportation Research Board published a Transportation Research Circular this month that outlines why this need is so great.
The authors from the Ottawa-based Traffic Injury Research Foundation cite several reasons for more research:
- Marijuana availability has greatly increased with the legalization of this drug in a growing number of jurisdictions.
- Marijuana is being sold legally in a variety of forms and potency since there is no standard dosage.
- Marijuana is the most commonly detected illicit drug in fatally injured drivers.
The circular also includes a description of why understanding marijuana’s effects on impairment are so difficult to pin down – because how it manifests in individuals depends on a variety of factors including the form of marijuana, potency of marijuana, frequency of use, and physical characteristics of the individual. The primary psychoactive ingredient in marijuana – THC -- is stored in the fat cells of the body so the rate at which it is released can vary. Moreover, the form of marijuana can determine when impairment starts and for how long it lasts. This is in contrast to alcohol, which is water soluble, and is eliminated from the body at a relatively constant rate that is well known and, therefore, can be more accurately measured.
The authors go on to note that the effects of alcohol and impairment have been studied for more than 60 years so the attributes of alcohol and its impact on people is well known. As a consequence, laws, enforcement, and policies to address alcohol impairment are well established. There is much work to be done before as much is known about marijuana.