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ISSN: 0033-3158 (printed version)
ISSN: 1432-2072 (electronic version)

Table of Contents


Volume 142 Issue 3 (1999) pp 295-301

original investigation: Specific attentional dysfunction in adults following early start of cannabis use

Hannelore Ehrenreich (1)(2), Thomas Rinn (1)(2), Hanns J. Kunert (1)(2), Manfred R. Moeller (3), Wolfgang Poser (1)(2), Lothar Schilling (4), Gerd Gigerenzer (5), Margret R. Hoehe (6)

(1) Departments of Psychiatry and Neurology, Georg August University, Göttingen, Germany
(2) Max Planck Institute for Experimental Medicine, Hermann-Rein-Strasse 3, D-37075 Göttingen, Germany e-mail:, Fax: +49-551-3899670
(3) Institute of Legal Medicine, State University of Saarland, Homburg, Germany
(4) Department of Neurosurgery, University Hospital, Mannheim, Germany
(5) Max-Planck-Institute for Human Development, Berlin, Germany
(6) Max-Delbrück-Center for Molecular Medicine, Berlin, Germany

Received: 15 June 1998/Final version: 30 September 1998

Rationale and objective: The present study tested the hypothesis that chronic interference by cannabis with endogenous cannabinoid systems during peripubertal development causes specific and persistent brain alterations in humans. As an index of cannabinoid action, visual scanning, along with other attentional functions, was chosen. Visual scanning undergoes a major maturation process around age 12-15 years and, in addition, the visual system is known to react specifically and sensitively to cannabinoids. 
Methods: From 250 individuals consuming cannabis regularly, 99 healthy pure cannabis users were selected. They were free of any other past or present drug abuse, or history of neuropsychiatric disease. After an interview, physical examination, analysis of routine laboratory parameters, plasma/urine analyses for drugs, and MMPI testing, users and respective controls were subjected to a computer-assisted attention test battery comprising visual scanning, alertness, divided attention, flexibility, and working memory. 
Results: Of the potential predictors of test performance within the user group, including present age, age of onset of cannabis use, degree of acute intoxication (THC+THCOH plasma levels), and cumulative toxicity (estimated total life dose), an early age of onset turned out to be the only predictor, predicting impaired reaction times exclusively in visual scanning. Early-onset users (onset before age 16; n = 48) showed a significant impairment in reaction times in this function, whereas late-onset users (onset after age 16; n = 51) did not differ from controls (n = 49). 
Conclusions: These data suggest that beginning cannabis use during early adolescence may lead to enduring effects on specific attentional functions in adulthood. Apparently, vulnerable periods during brain development exist that are subject to persistent alterations by interfering exogenous cannabinoids.

Key words Cannabinoids · Neuropsychology · Visual scanning · Attentional function · Development

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Online publication: March 4, 1999
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