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

BACKGROUND: 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. AIMS: We aim to develop and validate a prototype for a mobile phone application to measure ∆9-tetrahydrocannabinol-induced cognitive impairment.
METHODS: 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.
RESULTS: ∆9-Tetrahydrocannabinol-induced impairment was detected on most of the computer tasks, but was not evident on most of the phone tasks.
CONCLUSIONS: 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.