Marijuana
Said to be one of the least understood of all the natural drugs, marijuana has been known to man for nearly 5,000 years. Studies demonstrate that the drug can impair performance on simJ)le iTltellectual and psychomotor tests. The physiological and psychological effects of a single inhaled dose of marijuana appear to reach maximum intensity within half an hour of inhalation, to diminish after one hour and dissipate after three. Studies have shown that marijuana users, when introducing friends to the drug, "teach" them to notice subtle effects on consciousness. Two investigators describe the case of one subject who said he had some memory problems while driving an automobile under the influence of marijuana: "My reflexes and perception seem to be O.K., but I have problems like this: I'll come to a stop light and have a moment of panic because I can't remember whether or not I've just put my foot on the brake. Of course, when 1 look down, it's there, but in the second or two afterwards I can't remember having done it. In a similar way, I can't recall whether I've passed a turn I want to take or even whether I've made the turn. So all this difficulty must have something to do with some aspect of memory." Two effects of the drug indicate some change taking place in the brain during a marijuana "high." First, there is simple forgetting momentarily of what one has done or is going to do or say. Second, there is a tendency to go off on tangents because the line of thought is lost.
