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May 22/29, 2002

Does Marijuana Use Cause Long-term Cognitive Deficits?

Author Affiliations

Stephen J.LurieMD, PhD, Senior EditorIndividualAuthor

JAMA. 2002;287(20):2652-2654. doi:10.1001/jama.287.20.2652

To the Editor: Dr Solowij and colleagues1 concluded that their findings "confirm that long-term heavy cannabis users show impairments in memory and attention that endure beyond the period of intoxication." In his accompanying Editorial, Dr Pope2 pointed out that this study could not establish a causal relationship between use of marijuana and later declines in cognitive performance. Neither Solowij et al nor Pope, however, referred to laboratory studies designed to assess causality, such as ours, which evaluated the effects of acute marijuana administration on complex cognitive performance in regular marijuana smokers.3 Unlike the subjects of Solowij et al, these individuals were not seeking treatment and had heavier marijuana use, averaging 24 marijuana cigarettes per week. Participants smoked a single marijuana cigarette during 3 separate outpatient sessions containing varying amounts of tetrahydrocannabinol, which had minimal effects on cognitive functioning. Chait4 reported similar findings.