Citation

Ramaekers JG, Kauert G, van Ruitenbeek P, Theunissen EL, Schneider E, Moeller MR. Neuropsychopharmacology 2006; 31(10): 2296-2303.

Affiliation

Experimental Psychopharmacology Unit, Department of Neurocognition, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands. j.ramaekers@psychology.unimaas.nl

Comment In:

Neuropsychopharmacology 2006;31(12):2798-9; author reply 2800-1

Copyright

(Copyright © 2006, Nature Publishing Group)

DOI

10.1038/sj.npp.1301068

PMID

16572123

Abstract

Human performance studies have usually relied on low-potency marijuana (4% THC) for determining THC-induced impairment. The present study was designed to assess the effects of high-potency marijuana (13% THC) on human performance. In all, 20 recreational users of marijuana participated in a double-blind, placebo controlled, three way cross-over study. The treatments consisted of single doses of 0, 250, and 500 microg/kg THC. Performance tests were conducted at regular intervals between 15 min and 6 h postsmoking and included measures of motor control (Critical tracking task), executive function (Tower of London) motor impulsivity (Stop signal task), and risk taking (Iowa gambling task). THC significantly impaired performance in the Critical tracking task and decreased the number of correct decisions in the Tower of London task. In addition, THC significantly increased stop reaction time and the proportions of commission and omission errors in the Stop signal task. THC-induced impairments lasted up to 6 h postsmoking as indicated by the absence of a THC x Time after smoking interaction. Effect sizes for performance impairments produced by THC 250 microg/kg were relatively low but generally increased by a factor of two in case of THC 500 microg/kg. These data suggest that high potency marijuana consistently impairs executive function and motor control. Use of higher doses of THC in controlled studies may offer a reliable indication of THC induced impairment as compared to lower doses of THC that have traditionally been used in performance studies.

Language: en