(Randall 47). The most significant of these substances is 1-delta-9-tetrahydrocannabinol, an oily, water-insoluble liquid. In popular writing it is often called simply THC. The THC content of marijuana generally varies from 0.5% to 6%. Patterns of UseThere are many different cannabis preparations that are widely used to obtain effects. Cannabis may be either smoked or taken by mouth. However the same dose of THC is about three times as effective when smoked as when ingested (Randall 48). In the United States marijuana is usually smoked in the form of a hand-rolled cigarette (“joint” or “reefer”), but it is also smoked in a variety of pipes. Until the 1960’s the pattern in the United States was one of intermittent use of marijuana on social occasions by a relatively small number of young adults, together with regular use by some jazz musicians, urban minority groups, and Mexican Americans in the Southwest (Roffman 51). In the following years, however, marijuana use increased sharply. By 1979, 68% of young adults 18 to 25 had tried marijuana at least once, 35% had used it in the month just before the survey, and about 2/3 of current users reported using it five or more times per month. About 9% of users reported use on a daily basis. The use of marijuana also increased sharply in other countries throughout the world. Psychological and Physiological EffectsTHC produces its actions primarily on the nervous system and on the heart and blood vessels. The effects depend on the dose, the route of administration, and on the degree of tolerance that has developed. Because individuals vary in the way they inhale the smoke and because marijuana varies in THC content, the amount of active THC that reaches the bloodstream during smoking varies greatly (Potter 110). Generally, smoking a marijuana cigarette with a 2% THC content (equivalent to about 20 mg taken orally) produces changes in mood, mental abili...
