@article{ref1,
title="Cognition and motor control as a function of Delta9-THC concentration in serum and oral fluid: limits of impairment",
journal="Drug and alcohol dependence",
year="2006",
author="Ramaekers, Johannes Gerardus and Moeller, M. R. and van Ruitenbeek, Peter and Theunissen, Eef L. and Schneider, Erich and Kauert, G.",
volume="85",
number="2",
pages="114-122",
abstract="Cannabis use has been associated with increased risk of becoming involved in traffic accidents; however, the relation between THC concentration and driver impairment is relatively obscure. The present study was designed to define performance impairment as a function of THC in serum and oral fluid in order to provide a scientific framework to the development of per se limits for driving under the influence of cannabis. Twenty recreational users of cannabis participated in a double-blind, placebo-controlled, three-way cross-over study. Subjects were administered single doses of 0, 250 and 500 microg/kg THC by smoking. Performance tests measuring skills related to driving were conducted at regular intervals between 15 min and 6h post smoking and included measures of perceptual-motor control (Critical tracking task), motor impulsivity (Stop signal task) and cognitive function (Tower of London). Blood and oral fluid were collected throughout testing. Results showed a strong and linear relation between THC in serum and oral fluid. Linear relations between magnitude of performance impairment and THC in oral fluid and serum, however, were low. A more promising way to define threshold levels of impairment was found by comparing the proportion of observations showing impairment or no impairment as a function of THC concentration. The proportion of observations showing impairment progressively increased as a function of serum THC in every task. Binomial tests showed an initial and significant shift toward impairment in the Critical tracking task for serum THC concentrations between 2 and 5 ng/ml. At concentrations between 5 and 10 ng/ml approximately 75-90% of the observations were indicative of significant impairment in every performance test. At THC concentrations >30 ng/ml the proportion of observations indicative of significant impairment increased to a full 100% in every performance tests. It is concluded that serum THC concentrations between 2 and 5 ng/ml establish the lower and upper range of a THC limit for impairment.  Keywords: Cannabis impaired driving <p /> <p>Language: en</p>",
language="en",
issn="0376-8716",
doi="10.1016/j.drugalcdep.2006.03.015",
url="http://dx.doi.org/10.1016/j.drugalcdep.2006.03.015"
}