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Marijuana, alcohol and actual driving performance
Author(s) -
Ramaekers J. G.,
Robbe H. W. J.,
O'Hanlon J. F.
Publication year - 2000
Publication title -
human psychopharmacology: clinical and experimental
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.461
H-Index - 78
eISSN - 1099-1077
pISSN - 0885-6222
DOI - 10.1002/1099-1077(200010)15:7<551::aid-hup236>3.0.co;2-p
Subject(s) - alcohol , placebo , blood alcohol , crossover study , ethanol , anesthesia , poison control , headway , medicine , psychology , zoology , chemistry , injury prevention , simulation , computer science , biology , biochemistry , alternative medicine , environmental health , pathology
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 Δ 9 ‐tetrahydrocannabinol (THC) doses of 0, 100 and 200 μg/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). 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 μg/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 μg/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. Copyright © 2000 John Wiley & Sons, Ltd.