A most important variable encountered when evaluating the effect of marihuana is the interaction of the drug with the non-drug factors, set and setting. Set refers to the drug-taker's biological make-up including personality, past drug experiences, personal expectations of drug effect, and mood at the time of the drug experience. Setting refers to the external surroundings and social context in which the individual takes the drug. Set and setting exert their largest effect on psychoactive drugs, like marihuana, with subtle subjective mental effect and minimal physiological effect. Set and setting exert a variable but often marked influence on the potential drug effects (Waskow et al., 1970; Wickler, 1970).

The results of a series of experiments by Jones (1971) suggests the subjective state produced by "a socially relevant dose of smoked marihuana.... 9mg THC" is determined more by set and setting than by the THC content of the marihuana.

In one experiment, a greater variety and more intense pleasurable symptoms occurred in a fourman group allowing unstructured interpersonal interaction than in unstructured solitary test situations. Contrasting behavioral patterns were observed by the investigator and reported subjectively by the individuals. Subjects tested individually demonstrated a relaxed, slightly drowsy, undramatic state as they read, listened to the radio, or sit doing nothing. In the group setting there was elation, euphoria, uncontrolled laughter, a marked lack of sedation and much conversation. (Jones, 1971)

This strongly emphasizes the importance of setting in the marihuana experience. The reason is apparent why marihuana is usually used with other people. However, most investigators studying its effects evaluate their subjects alone, in well-controlled, sterile, scientific laboratories.

The importance of the placebo effect (the subject experiences a drug effect from an inert material) to the "social high" obtained from marihuana was studied in another experiment (Jones and stone, 1970; Jones, 1971). Misjudgments of the pharmacologic potency of both the smoked placebo (marihuana without THC) and active marihuana were commonly made by the subjects although physiologic and performance indices routinely matched the distinction correctly. The smoking of a material that smells and tastes like marihuana by individuals with marihuana experience appeared to produce a mental state that is interpreted as being high if combined with the expectation of becoming high.

The importance of learning to get high was demonstrated when individuals who smoked marihuana less than twice a month were compared with those who used marihuana at least seven times a week. Although both groups rated the active marihuana equally potent, the frequent users rated the placebo equally to the active drug, while the infrequent users experienced significantly less high from the placebo.

The infrequent users' experiences appears to reflect mainly pharmacologic factors with moderate set-setting influence. However, the frequent users' response to the placebo appears to reflect mainly learned set-setting influence and minimal pharmacologic factors. (Jones, 1971)

Smith and Mehl (1970) call learning to get high " reverse tolerance." During the early exposures to marihuana the individual learns to appreciate the subtle drug effect with repeated experience with the drug. Consequently, less drug may be required to experience the desired high in the early stages of marihuana use.

Further evidence for this is seen when the familiar smoking route and smell and taste cues are made ineffective by giving the active and inactive material by the oral route (Jones and Stone, 1970). Both groups of users can significantly distinguish the intoxication produced by 25mg of active material. But the frequent user rates this high significantly poorer than his smoking high while the infrequent user rates them correctly.