Toward developing conceptual and operational definitions for research on driving under the influence of cannabis

Abstract

Rationale

Cannabis liberalization has stimulated public and academic interest in whether cannabis impairs driving. As access to cannabis for research purposes has relaxed, the number of studies focused on this topic has grown considerably. However, synthesizing, translating and applying research findings focused on driving under the influence of cannabis (DUIC) is complicated by the absence of a standard definition of “impairment,” as well as the absence of a theoretical framework to guide converging evidence.

Objectives

In this theoretical essay, we aim to bring attention to, and help resolve, conceptual and operational issues that arise in defining “impairment.” We also aim to explain how target constructs within the DUIC literature relate to one another and provide a theoretical account of how driving is affected by cannabis.

Results

First, we propose three guiding principles for conceptually and operationally defining impaired driving and related concepts. These include considering the distinctions between drug effects and impaired driving; the distinctions between driving performance and driver behaviour; and, parallels between motor vehicle crashes and other forms of accident. Then, we introduce an adapted theoretical framework, based on prior theories focused on normal driver behaviour, to link research findings and provide an account of how cannabis affects driving.

Conclusions

Within the DUIC literature there is an assortment of related, but distinct, concepts pertaining to impaired driving. We suggest terminology, definitions and a theoretical framework so researchers, stakeholders, policy makers and the public can share a common understanding of how cannabis affects driving.