The Hidden Dangers of Cannabis for Older Drivers

There is a large and growing population of individuals aged over 65 in the United States, many of whom drive automobiles. Elements of aging may adversely impact driving ability; in some individuals, mild cognitive impairment and early dementia are responsible for further deterioration. Older drivers have more crashes per mile driven and are more likely to be injured or die in crashes of similar magnitude. At the same time, an increasing number of older people are using cannabis for medical and recreational purposes. Cannabis (mostly due to its delta-9 tetrahydrocannabinol [THC] content) compromises sensory and neurocognitive abilities necessary for safe driving, and acute use is associated with an increased rate of motor vehicle crashes, including fatal ones. Evidence suggests that older individuals are more likely to be impaired by cannabis, possibly reflecting altered THC metabolism (due to changes in bodily composition and pharmacokinetics), as well as age-related changes in neurocognitive function and in the brain's endocannabinoid system. Consequently, older drivers who use cannabis may be at substantially increased risk of involvement in motor vehicle crashes. Despite this confluence of age-related factors, the amount of research on cannabis' effects on the driving ability of older adults is negligible, and public health messaging related to this situation is lacking. We suggest that more attention be paid to this topic.