Levels of processing and acute effects of marijuana on memory.

Subjects' memory for lists of words was tested following the smoking of a single marijuana cigarette containing 1.4% delta 9-THC or a placebo cigarette. During list presentation, each word was preceded by an orienting question which required one of four types of linguistic information (orthographic, phonetic, semantic, or syntactic). Free recall tests were administered immediately after each list (IFR) and following IFR for all five lists (FFR). Results indicated that subjects recalled fewer words while intoxicated with marijuana. There was no interaction between drug condition and level of processing in IFR, but a complex relationship mediated by time was seen in FFR. Drug subjects were more likely to forget meaningfully processed words on recently presented lists. The data provided little support for the hypothesis that marijuana differentially affects the processing and retention of different types of linguistic information.