Effects of Δ-THC on Working Memory: Implications for Schizophrenia?

Abstract

This article reviews the literature on the acute effects of Delta 9-tetrahydrocannabinol, the primary psychoactive component of marijuana, on working memory, and the implications for schizophrenia. Working memory deficits are a hallmark feature of schizophrenia, and have been implicated as an etiologic mechanism contributing to the onset of the disorder. Regular marijuana smokers may also exhibit subtle working memory impairment relative to healthy controls, and an association between marijuana abuse and subsequent development of schizophrenia, though controversial, has been reported in the literature. The causal role that marijuana plays in working memory impairment related to schizophrenia, however, remains unclear. Thus, this article specifically considers the acute effects of marijuana on working memory performance. The ecologic relevance and clinical significance of these findings will be examined, and directions for future research will be recommended.

FIGURE. MEAN SUBJECTIVE-EFFECTS RATINGS (LEFT PANEL) AND MEAN HEART RATE (RIGHT PANEL) AS A FUNCTION OF Δ⁹-THC CONCENTRATION AND TIME*

* Error bars represent one SEM. Δ⁹-THC=Delta 9-tetrahydrocannabinol; min=minutes; BPM=beats per minute; SEM= standard error of measurement. Hart CL, van Gorp W, Haney M, Foltin RW, Fischman MW. Effects of acute smoked marijuana on complex cognitive performance. Neuropsychopharmacology. 2001;25(5):757–765. Adapted with permission from Nature Publishing Group. Copyright 2001.