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Psychopharmacology (Berl). 2009 May;204(1):85-94. doi: 10.1007/s00213-008-1440-0. Epub 2008 Dec 20.

Cognitive and psychomotor effects in males after smoking a combination of tobacco and cannabis containing up to 69 mg delta-9-tetrahydrocannabinol (THC).

Author information

1
National Poisons Information Center, National Institute for Public Health and the Environment, Bilthoven, The Netherlands. claudine.hunault@rivm.nl

Abstract

RATIONALE:

Delta(9)-Tetrahydrocannabinol (THC) is the main active constituent of cannabis. In recent years, the average THC content of some cannabis cigarettes has increased up to approximately 60 mg per cigarette (20% THC cigarettes). Acute cognitive and psychomotor effects of THC among recreational users after smoking cannabis cigarettes containing such high doses are unknown.

OBJECTIVES:

The objective of this study was to study the dose-effect relationship between the THC dose contained in cannabis cigarettes and cognitive and psychomotor effects for THC doses up to 69.4 mg (23%).

MATERIALS AND METHODS:

This double-blind, placebo-controlled, randomised, four-way cross-over study included 24 non-daily male cannabis users (two to nine cannabis cigarettes per month). Participants smoked four cannabis cigarettes containing 0, 29.3, 49.1 and 69.4 mg THC on four exposure days.

RESULTS:

The THC dose in smoked cannabis was linearly associated with a slower response time in all tasks (simple reaction time, visuo-spatial selective attention, sustained attention, divided attention and short-term memory tasks) and motor control impairment in the motor control task. The number of errors increased significantly with increasing doses in the short-term memory and the sustained attention tasks. Some participants showed no impairment in motor control even at THC serum concentrations higher than 40 ng/mL. High feeling and drowsiness differed significantly between treatments.

CONCLUSIONS:

Response time slowed down and motor control worsened, both linearly, with increasing THC doses. Consequently, cannabis with high THC concentrations may be a concern for public health and safety if cannabis smokers are unable to titrate to a high feeling corresponding to a desired plasma THC level.

TRIAL REGISTRATION:

ClinicalTrials.gov NCT00225407.

PMID:
19099294
DOI:
10.1007/s00213-008-1440-0
[Indexed for MEDLINE]
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