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Neurocognitive performance during acute THC intoxication in heavy and occasional cannabis usersDepartment of Neuropsychology and Psychopharmacology, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands j.ramaekers{at}psychology.unimaas.nl
Department of Forensic Toxicology, Institute of Legal Medicine, Goethe University of Frankfurt, Frankfurt, Germany
Department of Neuropsychology and Psychopharmacology, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands
Department of Forensic Toxicology, Institute of Legal Medicine, Goethe University of Frankfurt, Frankfurt, Germany
Unikliniken des Saarlandes, Homburg, Germany Abstract
Performance impairment during
Key Words: cannabis use history • cognition • impulsivity • performance • THC • tolerance
This version was published on May
1, 2009 Journal of Psychopharmacology, Vol. 23, No. 3,
266-277 (2009) |
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9-tetrahydrocannabinol (THC) intoxication has been well described in occasional cannabis users. It is less clear whether tolerance develops to the impairing effects of THC in heavy users of cannabis. The aim of the present study was to assess neurocognitive performance during acute THC intoxication in occasional and heavy users. Twenty-four subjects (12 occasional cannabis users and 12 heavy cannabis users) participated in a double-blind, placebo-controlled, two-way mixed model design. Both groups received single doses of THC placebo and 500 µg/kg THC by smoking. Performance tests were conducted at regular intervals between 0 and 8 h after smoking, and included measures of perceptual motor control (critical tracking task), dual task processing (divided attention task), motor inhibition (stop signal task) and cognition (Tower of London). THC significantly impaired performance of occasional cannabis users on critical tracking, divided attention and the stop signal task. THC did not affect the performance of heavy cannabis users except in the stop signal task, i.e. stop reaction time increased, particularly at high THC concentrations. Group comparisons of overall performance in occasional and heavy users did not reveal any persistent performance differences due to residual THC in heavy users. These data indicate that cannabis use history strongly determines the behavioural response to single doses of THC.