Alignment of subjective and objective driving impairment following alcohol and cannabis use: A systematic review

Abstract

This systematic review investigated the alignment of objective and subjective driving impairment following alcohol and cannabis administration. Under PRISMA guidelines, a literature search was conducted on various research databases. Studies (N = 20) were included if they were within-subjects designs, included acute alcohol or cannabis administration, and implemented both objective and subjective measures of driving performance. The review revealed that although the current evidence was limited, there was an apparent (albeit inconsistent) alignment between subjective and objective measures of driving impairment for both alcohol and cannabis conditions. Notably, preliminary evidence suggested that heavier alcohol users may be inclined to underestimate their impairment, whilst cannabis users may overestimate the level of their impairment. However, the current literature was considered limited due to the absence of adequate analytical support, the simplistic (and potentially misleading) approaches to measuring impairment, and the lack of inquiry into how interpersonal differences mediate the subjective-objective relationship.