Tetrahydrocannabinol (THC) impairs encoding but not retrieval of verbal information.
Cannabis and agonists of the brain cannabinoid receptor (CB Healthy subjects were recruited from the community. Subjects were administered the Rey-Auditory Verbal Learning Test (RAVLT) either before administration of THC (experiment 1) (n38) or while under the influence of THC (experiment 2) (n57). Immediate and delayed recall on the RAVLT was compared. Subjects received intravenous THC, in a placebo-controlled, double-blind, randomized manner at doses known to produce behavioral and subjective effects consistent with cannabis intoxication. Total immediate recall, short delayed recall, and long delayed recall were reduced in a statistically significant manner only when the RAVLT was administered to subjects while they were under the influence of THC (experiment 2) and not when the RAVLT was administered prior. THC acutely interferes with encoding of verbal memory without interfering with retrieval. These data suggest that learning information prior to the use of cannabis or cannabinoids is not likely to disrupt recall of that information. Future studies will be necessary to determine whether THC impairs encoding of non-verbal information, to what extent THC impairs memory consolidation, and the role of other cannabinoids in the memory-impairing effects of cannabis. Cannabinoids, Neural Synchrony, and Information Processing (THC-Gamma) httpclinicaltrials.govct2showstudyNCT00708994 NCT00708994 Pharmacogenetics of Cannabinoid Response httpclinicaltrials.govct2showNCT00678730 NCT00678730.