Driving sober is crucial for the safety of the drivers and the safety of the people in our communities. A recent study from McLean Hospital’s Cognitive and Clinical Neuroimaging Core and the Marijuana Investigations for Neuroscientific Discovery program (MIND) may influence our current understanding of sobriety in relation to cannabis use.
The study, published in January 2020, found that regular long-term cannabis use has negative effects on an individual’s driving ability, even after they have already sobered up. The findings also report that individuals who started their cannabis use before age 16 were even more impaired than those who began recreational use after age 16.
The research team enlisted a total of 45 participants, who were required to have valid driver’s licenses and were evaluated with various tests, including an IQ test and the Barrett Impulsivity Scale-II (BIS). The BIS measures impulsivity in the participants’ attention, motor, and non-planning abilities.
The participants were split into two groups: the chronic use group (28 participants) and the non-user control group (17 participants).
The chronic users were eligible to participate if they use cannabis at least five days a week, had previously used cannabis at least 1,500 times in their lifetimes, and tested positive for cannabinoids from a urine sample. They were then assessed for any other underlining substance-use disorders and were not able to participate if anything other than a cannabis-use disorder was present.
The chronic use group was split further into two groups, one group of cannabis users who started using before 16 (14 participants) and the other consisting of cannabis users who started after 16 (14 participants). They reported what kind of cannabis products they use (e.g. pills, edibles, joints, etc.), their preferred method of use (e.g. vaping, smoking, etc.), their frequency of use, and the dosage they commonly take.
Finally, they were asked to abstain from any form of cannabis use for at least 12 hours before the experiment was conducted and reported their symptoms using a Marijuana Withdrawal Checklist containing 16 criteria to be ranked during the abstinence period.
The experiment began with all participants undertaking another urine test to ensure they abstained for the proper amount of time. Then, the participants used a driving simulator for a 10-minute period in order to measure how they conduct themselves on the road. The simulation included both rural and urban driving conditions and required the participants to obey all the laws of the road as they would normally do in the real world.The simulation took note of any of the participants’ violations such as accidents, traffic sign violations, speed limit violations, and lane violations.
The research team found that the chronic user group scored higher in the attention and non-planning categories of the BIS, meaning they are more impulsive in these domains. In the driving simulation, the user group was far more impaired than the non-user group and had more collisions, more missed stops, more centerline crosses, and drove at greater speeds than the non-users. The early and late user groups performed very similarly on the preliminary tests, but the early user group performed even more poorly than the late user group.
The results from this study show that recreational cannabis use has noticeable lasting effects on the brain even when the substance is not present in the body. Their findings also show that cannabis use before age 16 leads to more impaired driving abilities.
The findings of the present study show a possible link between early-onset cannabis use and increased impulsive driving, especially when other research in this area is factored in. Further research is needed to truly figure out if early cannabis use has any direct negative effects on brain development.