Mendelson et al. (1972), under contract to the Commission, analyzed the effects on behavior of acute marihuana intoxication on an extensive variety of assessine nts including a simple operant task, mood states, individual and group observations before, during and after smoking and clinical psychological evaluations.

Sleep-inducing properties were confirmed. Increased amounts of total sleep were observed in both number and length of shorter and longer blocks of consecutive hours of sleep related to marihuana smoking.

Examination of mood assessments prior, during and after marihuana smoking indicates that the acute effects were a reduction of negative moods (anxiety, hostility, and guilt-shame) and an increase in the positive moods (carefreeness and friendliness). Examinations of the mood prior to smoking revealed that the subjects tended to smoke marihuana when they reported generally positive moods. The effect of the drug was to increase this positive mood. One paradoxical finding was that the subjects also reported feeling more depressed after smoking.

Acute effects of marihuana on cognitive and motor functions were studied with a battery of tests sensitive to brain function (Halstead Category Test, Tactile Performance Test, Seashore Rhythm Test, Finger Tapping Test, Trail Making Test and the Weschler Adult Intelligence Scale). No alterations in performance as a result of acute intake of marihuana were noted in any of these.

The acute effect of marihuana smoking on social behavior was investigated, by observing the individual and his interaction in small groups. The data indicated very strongly that marihuana smoking, in addition to being a subjective drug experience, is also a social activity around which verbal interaction and other types of social behavior are centered.

Although marihuana smoking tended to be, a group activity, subjects did not always engage in verbal communication while smoking. Subjects often were observed withdrawing from the social interaction and then participating in some type of noncommunicative passive activity, such as watching television, listening to music, reading or staring at objects or people. This decrement in total interaction appeared to be a drug effect.

Heavy marihuana users tended to be more withdrawn than the intermittent users, often listening to the stereo and focusing on the personal effects of the drug. The intermittent users tended to watch television which provided group entertainment, thus enhancing the social effects of the drug.

Verbal interaction in formal task-oriented discussion groups diminished when several group members were simultaneously intoxicated. How-ever, groups engaged in problem-solving tasks performed more efficiently because less suggestions and discussion ensued before proposing a workable solution. The groups tended to become more convivial and less task-oriented although none failed to arrive, at the goal. Marihuana did not appear to increase hostility during these sessions and furthermore tended to change the nature of hostile communication from direct criticism to indirect sarcasm.

Assessment of risk-taking behavior revealed that under the influence of marihuana, users tend to become more conservative in the decision making.

In summary, it appears that marihuana does exert subtle effects on measurable components of social behavior and interaction.