Memory & Concentration

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Dutch study

dpa German Press Agency
Published: Sunday November 5, 2006

Amsterdam- Occasional and moderate abuse of the drugs cannabis and ecstasy does not lead to long-term memory impairment or affect ability to concentrate, according to a study conducted at Utrecht University in the Netherlands. The findings are contained in a doctoral thesis by Gerry Jager, who conducted her research in combination with the Academic Medical Centre in Amsterdam.

"Occasional use of ecstasy (an average of a total of two pills) or frequent cannabis use (several marijuana cigarettes a week over a period of an average of four years) does not lead to long-term abnormalities in memory or ability to concentrate, or related brain activity," Jager found.

She did, however, note that other studies suggested that "frequent and sustained use of the party drug ecstasy" did hold risks for long- term memory.

Jager studied the long-term effects of ecstasy and cannabis on the brain functions memory and ability to concentrate using functional magnetic resonance imaging (FMRI).

The neuro-psychologist invited volunteers aged 18 to 35 with experience of drugs to participate.

The study focused on drug users who regularly took amphetamines (speed) or cocaine but only rarely ecstasy. It then compared results from tests on them with findings on regular ecstasy users.

The subjects were required to abstain from drugs for two weeks ahead of the test and alcohol for one week. Compliance was checked through urine and hair samples. They received financial recompense for their cooperation.

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Journal of Psychopharmacology | 1 May 09
Neurocognitive performance during acute THC intoxication in heavy and occasional cannabis users



JG Ramaekers

Department of Neuropsychology and Psychopharmacology, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands j.ramaekers@psychology.unimaas.nl

G Kauert

Department of Forensic Toxicology, Institute of Legal Medicine, Goethe University of Frankfurt, Frankfurt, Germany

EL Theunissen

Department of Neuropsychology and Psychopharmacology, Faculty of Psychology, Maastricht University, Maastricht, The Netherlands

SW Toennes

Department of Forensic Toxicology, Institute of Legal Medicine, Goethe University of Frankfurt, Frankfurt, Germany

MR Moeller

Unikliniken des Saarlandes, Homburg, Germany

Abstract

Performance impairment during {Delta}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.

Key Words: cannabis use history • cognition • impulsivity • performance • THC • tolerance

This version was published on May 1, 2009

<small>Journal of Psychopharmacology, Vol. 23, No. 3, 266-277 (2009)
DOI: 10.1177/0269881108092393</small>