Citation

Ramaekers JG, Robbe HWJ, O'Hanlon JF. Hum. Psychopharmacol. 2000; 15(7): 551-558.

Affiliation

Behavior Institute, Maastricht University, The Netherlands.

Copyright

(Copyright © 2000, John Wiley and Sons)

DOI

10.1002/1099-1077(200010)15:7<551::AID-HUP236>3.0.CO;2-P

PMID

12404625

Abstract

The objective of the current study was to assess the separate and combined effects of marijuana and alcohol on actual driving performance. Eighteen subjects were treated with drugs and placebo according to a balanced, 6-way, crossover design. On separate evenings they were given weight calibrated Delta(9)-tetrahydrocannabinol (THC) doses of 0, 100 and 200 micro-g/kg with and without an alcohol dose sufficient for achieving blood alcohol concentrations (BAC) of 0.04 g/dl while performing a Road Tracking and Car Following Test in normal traffic. Main outcome measures were standard deviation of lateral position (SDLP), time driven out of lane (TOL), reaction time (RT) and standard deviation of headway (SDH) [close following]. Both THC doses alone, and alcohol alone, significantly impaired the subjects performances in both driving tests. Performance deficits were minor after alcohol and moderate after both THC doses. Combining THC with alcohol dramatically impaired driving performance. Alcohol combined with THC 100 and 200 micro-g/kg produced a rise in SDLP the equivalent of that associated with BAC=0.09 and 0.14 g/dl, respectively. Mean TOL rose exponentially with SDLP. Relative to placebo mean RT lengthened by 1.6 s under the combined influence of alcohol and THC 200 micro-g/kg. Changes in SDH ranged between 0.9 and 3.8 m. Low doses of THC moderately impair driving performance when given alone but severely impair driving performance in combination with a low dose of alcohol.

Keywords: Cannabis impaired driving; Ethanol impaired driving

Language: en