Developing a phone-based measure of impairment after acute oral ∆9-tetrahydrocannabinol.

Two double-blind, within-subjects studies tested whether a mobile phone app could detect cognitive impairment from oral doses of ∆9-tetrahydrocannabinol (0, 7.5, 15 mg). In 24 healthy non-daily cannabis users per study, tasks measuring cognitive speed, reaction time, fine motor ability, working memory, and time perception were completed during four-hour sessions at peak drug effect. ∆9-Tetrahydrocannabinol impaired performance on most standardized computer tasks but not on most brief phone tasks. The phone tasks' brevity likely reduced their sensitivity. The findings confirm impairment at two recreational doses but raise doubts about developing a phone-based field sobriety test for cannabis.

Study at a glance

Abstract

Acute consumption of cannabis or its primary psychoactive ingredient ∆9-tetrahydrocannabinol has been shown to impair memory, reaction time, time perception, and attention. However, it is difficult to measure these impairments in a brief test that can be used in a non-laboratory setting. We aim to develop and validate a prototype for a mobile phone application to measure ∆9-tetrahydrocannabinol-induced cognitive impairment. We conducted two double-blind, within-subjects studies examining impairments after oral doses of ∆9-tetrahydrocannabinol (0, 7.5, 15 mg) using both standardized computer-based tasks and our novel phone-based tasks. The tasks measured cognitive speed, reaction time, fine motor ability, and working memory and, in the second study, time perception. Study 1 (n=24) provided initial data, and Study 2 (n=24) was designed to refine the measures. In both studies, healthy non-daily cannabis users participated in three four-hour experimental sessions in which they received capsules containing ∆9-tetrahydrocannabinol (7.5, 15 mg) or placebo. Subjective and cardiovascular measures were obtained at regular intervals, and at the time of peak drug effect subjects completed both standardized, computer-based and brief, phone-based tasks. ∆9-Tetrahydrocannabinol-induced impairment was detected on most of the computer tasks, but was not evident on most of the phone tasks. The phone tasks were brief, to facilitate use in a non-laboratory setting, but it is likely that this made them less sensitive to the impairing effects of ∆9-tetrahydrocannabinol. These findings confirm that ∆9-tetrahydrocannabinol impairs performance on several tasks at two recreationally relevant doses, but raises question about the feasibility of designing a phone application as a sensitive field sobriety test for cannabis.