Retrospective Event-Level Patterns of Cannabis-Impaired Driving

Cannabis-impaired driving (CID) is an increasing public health concern, particularly among emerging adults. Despite growing prevalence, little is known about episode-level patterns of use and impairment before driving. This study examined detailed features of recent and heaviest CID episodes to better understand high-risk driving contexts.

Participants were 149 emerging adult cannabis users (ages 18-29) reporting ≥3 instances of driving after cannabis use in the past 3 months. Event-level data were collected via retrospective self-report of the most recent and heaviest CID occasions. Participants reported method of use, amount consumed, wait time before driving, subjective intoxication, driving distance, alcohol co-use, and the presence of passengers. Paired-sample t tests examined within-person differences between episodes.

More than 60% reported actively using cannabis while driving, and more than one third reported driving after simultaneous cannabis and alcohol use. Passengers were present in 46% of the most recent driving episodes and 35% of the heaviest driving episodes. Subjective intoxication ratings were significantly higher during the heaviest episodes (M = 6.96) compared with the most recent episodes (M = 4.71, p < .001), yet wait time before driving and distance driven did not differ.

Findings highlight high-risk contexts in CID, including simultaneous substance use and driving while intoxicated, often with passengers present. Retrospective event-level analysis offers a nuanced understanding of CID behaviors and underscores the need for prevention strategies that address situational risk factors.