New research suggests that smoking cannabis negatively affects driving skills among those aged 65 years and older. The corresponding study was published in JAMA Network Open.
Studies suggest that cannabis use impairs driving skills and increases collision risk. Although cannabis use is increasing among older adults, research until now has largely involved younger participants. In the current study, researchers investigated how cannabis use may affect driving skills among older drivers.
To do so, they recruited 31 adults aged 65 to 79 years old who reported using cannabis for an average of 40 years. Overall, 25 participants reported recreational cannabis use, one medical use, and five both medical and recreational use. 24 participants reported using cannabis more than once per week for recreational purposes.
During the study, participants were asked to operate a driving simulator before, 30 minutes after, and 180 minutes after smoking their preferred strain of cannabis. Most participants chose cannabis strains with an average content of 18.74% tetrahydrocannabinol (THC) and 1.46% cannabidiol (CBD). The researchers assessed their driving skills via the simulator and took blood samples at various time points to determine their THC levels.
Ultimately, the researchers found that weaving increased and mean speed decreased at 30 minutes after smoking cannabis but not 180 minutes afterward. They further noted that blood THC increased 30 minutes after smoking, but that THC levels were not correlated with weaving or mean speed. Although driving skills appeared unaffected at 180 minutes, participants rated their ability to drive as impaired at the same time point.
The researchers wrote that the findings suggest cannabis can impair driving in older adults and that older drivers should refrain from cannabis use when contemplating driving a motor vehicle.
They noted, however, that their findings have some limitations. As most of their participants were white, and over half were male, they wrote that larger sample sizes would be needed to conduct more rigorous analyses of the effects of sex and ethnicity. They further noted that the difference between participants' reported feelings about their driving ability and simulator results may indicate that the simulator had limited sensitivity for detecting more nuanced changes in driving.
Sources: EurekAlert, JAMA Network Open