State-dependent effects on memory and subjective classification were found in two of four tasks performed by experienced marihuana smokers. The dose of marihuana used (7.5 mg tetrahydrocannabinol content) was considerably less than used in other studies, and corresponded much more closely to a naturalistic "street use" dose.
As predicted by a state-dependent model, subjects reproduced material best when they were in the same drug state as they had been when they first encountered the material to be recalled. In particular, marihuana-marihuana reproduction surpassed marihuana-placebo or placebo-marihuana reproduction; that is, material first encountered in the drug state was better reproduced when the subject was again in the drug state than when he was sober. Marihuana did produce some overall impairment in performance; placebo-placebo reproduction was substantially better than marihuana-marihuana.
The phenomenon of state-dependence has been demonstrated for other widely used psychoactive drugs including alcohol, stimulants, and barbiturates, and may be a factor in their appeal as mind-changing agents.