marijuana
 
{mar-i-wahn'-uh}
 
   Marijuana (also spelled marihuana) is the common name given to any
DRUG preparation from the hemp plant, Cannabis sativa. Various forms of
this drug are known by different names throughout the world, such as kif
in Morocco, dagga in South Africa, and ganja in India. Hashish refers to a
dried, resinous substance that exudes from the flowering tops of the
plant. In Western culture, cannabis preparations have acquired a variety
of slang names, including grass, pot, tea, reefer, weed, and Mary Jane.
Cannabis has been smoked, eaten in cakes, and drunk in beverages. In
Western cultures marijuana is prepared most often as a tobaccolike mixture
that is smoked in a pipe or rolled into a cigarette.
 
    One of the oldest known drugs, cannabis was acknowledged as early as
2700 BC, in a Chinese manuscript. Throughout the centuries it has been
used both medicinally and as an intoxicant. The major psychoactive
component of this drug, however, was not identified until the mid-1960s;
this ingredient is tetrahydrocannabinol, commonly known as THC. At
present, other cannabinoids have been isolated and their possible
biochemical activities are being explored. Psychoactive compounds are
found in all parts of the male and female plant, with the greatest
concentration in the flowering tops. The content of these active compounds
varies greatly from plant to plant, depending on genetic and environmental
factors.
 
    Marijuana has its major physiological effects on the cardiovascular
and central nervous systems;  these effects are primarily sedative and
hallucinogenic.  Low doses psychologically produce a sense of well-being,
relaxation, and sleepiness.  Higher doses cause mild sensory distortions,
altered time sense, loss of short-term memory, loss of balance, and
difficulty in completing thought processes.  Even higher doses can result
in feelings of depersonalization, severe anxiety and panic, and a toxic
psychosis, along with hallucinations, loss of insight, delusions, and
paranoia. Physiologically, the heart rate increases and blood vessels of
the eye dilate, causing reddening.  A feeling of tightness in the chest
and a lack of muscular coordination may also occur. Research suggests that
marijuana smoke may have a long-term harmful effect on the lungs.  Users
may develop tolerance for the drug, but studies have not determined
whether physical dependence results.
 
    The use of marijuana as an intoxicant in the United States became a
problem of public concern in the 1930s.  Regulatory laws were passed in
1937, and criminal penalties were instituted for possession and sale of
the botanical drug.  In 1968 the possession and sale of THC, the
psychoactive chemical component, was restricted to research.  Despite
these measures, marijuana continued to be widely used in succeeding
decades as various groups sought to decriminalize its possession.  A
survey in the late 1970s indicated that at least 43 million Americans had
tried the drug.  In the 1980s, however, surveys of high school and college
students showed that marijuana use was steadily declining.  The number of
high school seniors for instance, who had tried the drug decreased from
50.8 percent in 1979 to 33.1 percent in 1989.
 
    Conversely, cultivation of marijuana in the United States is
increasing, accounting for 25 percent of the U.S.  domestic market by
1990.  Moreover, new growing practices have increased the potency (THC
content) of domestically produced marijuana five fold or more, causing
concern among drug-abuse experts about adverse effects from higher THC
doses.
 
    Medically, marijuana and THC preparations are sometimes used to treat
GLAUCOMA, because they help to reduce pressure within the eye.  In 1985
the Food and Drug Administration also approved the use of synthetic THC
(dronabinol) for treating the nausea and vomiting that can accompany
cancer chemotherapy.  It apparently acts by binding to opiate receptors in
the medulla of the brain.
 
Charles W.  Gorodetzky
 
Bibliography:
Abel, Ernest L., A Marihuana Dictionary (1982); Gold, M.S., Marijuana
(1989);  Himmelstein, J.L., The Strange Career of Marihuana (1983); 
Kanzukol, Paul, and Musty, Richard, eds., Marijuana (1989); Nahas, Gabriel
G., Marihuana in Science and Medicine (1984).