The authors review and discuss the findings which they reported in Science, December 13, 1968. No human experiments with marijuana designed according to modern principles of drug testing had been previously performed.
The pharmacologic action of a drug is but one of three factors in its effect; the others are "set"the individual's expectations of what the drug will doand "setting" the total environment (physical and social) in which a drug is taken. Set and setting can overshadow pharmacologic action. Asking drug users what effect they get is grossly unreliable; on the other hand, laboratory studies must be designed so that, through environmental manipulation, an observed effect may be ascribed to a known cause (as the administration of a drug).