[Correction added on 21/11/2013, after first online publication: The missing dose of THC has been inserted, 300 μg·kg−1]
Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users
Article first published online: 14 NOV 2013
© 2013 The British Pharmacological Society
British Journal of Pharmacology
Special Issue: Themed Section: Neuropeptides. Guest Editors: Julie Keeble
Volume 170, Issue 7, pages 1410–1420, December 2013
How to Cite
van Wel, J. H. P., Kuypers, K. P. C., Theunissen, E. L., Toennes, S. W., Spronk, D. B., Verkes, R. J. and Ramaekers, J. G. (2013), Single doses of THC and cocaine decrease proficiency of impulse control in heavy cannabis users. British Journal of Pharmacology, 170: 1410–1420. doi: 10.1111/bph.12425
- Issue published online: 14 NOV 2013
- Article first published online: 14 NOV 2013
- Accepted manuscript online: 22 SEP 2013 08:07PM EST
- Manuscript Accepted: 13 AUG 2013
- Manuscript Revised: 5 AUG 2013
- Manuscript Received: 21 FEB 2013
- ZonMw, The Netherlands. Grant Number: 31160206
Background and Purpose
Cannabis is the most popular drug used in the European Union, closely followed by cocaine. Whereas cannabis impairs neurocognitive function in occasional cannabis users, such impairments appear less prominent in heavy users, possibly as a result of tolerance. The present study was designed to assess whether the impairing effects of Δ9-tetrahydrocannabinol (THC) in heavy cannabis users would present in a wide range of neuropsychological functions or selectively affect specific performance domains. We also assessed the acute effects of cocaine on neurocognitive functions of heavy cannabis users.
Heavy cannabis users, who had a history of cocaine use (n = 61), participated in a double-blind, placebo-controlled, three-way crossover study. Subjects received single doses of cocaine HCl (300 mg), cannabis (THC 3001 μg·kg−1) and placebo, and completed a number of tests measuring impulse control and psychomotor function.
Single doses of cannabis impaired psychomotor function and increased response errors during impulsivity tasks. Single doses of cocaine improved psychomotor function and decreased response time in impulsivity tasks, but increased errors.
Conclusions and Implications
Heavy cannabis users display impairments in a broad range of neuropsychological domains during THC intoxication. Impairments observed in psychomotor tasks, but not in impulsivity tasks, appeared smaller in magnitude as compared with those previously reported in occasional cannabis users. Heavy cannabis users were sensitive to the stimulating and inhibitory effects of cocaine on psychomotor function and impulsivity respectively. The reduction in proficiency in impulse control may put drug users at increased risk of repeated drug use and addiction.