Cannabis and psychomotor performance: A rational review of the evidence and implications for public policy

Abstract

A previous US government analysis estimated that among those who acknowledge having driven following the consumption of an illicit substance, a majority of respondents, 70%, affirm having done so following the ingestion of cannabis. [4] While this total is far from negligible, it is far fewer than the number of respondents who acknowledge having driven while under the influence of alcohol. The presence of cannabis’ primary psychoactive ingredient, delta-9-tetrahydrocannabinol (THC), or THC’s primary metabolite, carboxy THC, has frequently been identified in the blood or urine of drivers involved in fatal traffic accidents. [5] Explanations for this result are two-fold. First, cannabis is by far the most widely used illicit drug among the US population, with non-governmental polling data indicating that nearly one out of two Americans admit having tried it. [6] Second, cannabis is the illicit substance most readily detectable by toxicological tests. The presence of THC may be detectable in the blood of occasional cannabis consumers for several hours after past use. [7] In more chronic users, THC may be present at relatively low blood levels for a