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Pharmacology => Drug => Marijuana
Marijuana
Marijuana, mixture of leaves, stems, and flowering tops of the Indian hemp plant Cannabis sativa , smoked or eaten for its hallucinogenic and pleasure-giving effects. The psychoactive ingredient of marijuana, tetrahydrocannabinol (THC), is concentrated in the flowering tops of the plant. Hashish, a drug prepared from the plant resin, has about eight times more THC than marijuana. Marijuana grows throughout temperate regions, with the more potent varieties produced in dry, hot, upland climates.
Except for limited medical purposes, cultivating marijuana is illegal in all but a few countries. In the United States, possession and use of marijuana was legal only in the state of Alaska from 1975 until 1990, when voters approved a ballot measure that again made it illegal.
Known in Central Asia and China as early as 3000 BC, marijuana was used as a folk medicine. From about 1900 it was used as a pleasure-inducing drug and by the 1960s and 1970s its use was widespread. It became, after alcohol, the second most popular drug. Although marijuana has not been proven physically addicting and no physical withdrawal symptoms occur when use is discontinued, psychological dependence can develop with consistent, long-term use.
Many users describe two phases of marijuana intoxication: initial stimulation, which includes giddiness and euphoria, followed by sedation and pleasant tranquility. Mood changes are often accompanied by altered perceptions of time, space, and one's bodily dimensions. Thinking processes become disrupted by fragmentary ideas and memories. Many users report increased appetite, heightened sensory awareness, and feelings of pleasure. Negative effects can include confusion, acute panic reactions, anxiety attacks, fear, a sense of helplessness, and loss of self-control.
Chronic marijuana users may develop an amotivational syndrome characterized by passivity, decreased motivation, and preoccupation with taking drugs. The relationship of this syndrome to marijuana use, however, has not been established. Like alcohol intoxication, marijuana intoxication impairs judgment, comprehension, memory, speech, problem-solving ability, and reaction time. The effects of long-term use on the intellect are unknown. Evidence that marijuana induces or causes brain damage does not exist.
Medical research has indicated that the drug has potential medicinal value. In the most recent report, a controversial 1999 study commissioned by the United States federal government found that marijuana is effective in relieving pain, nausea, and the severe weight loss associated with acquired immune deficiency syndrome (AIDS). Moreover, this study confirmed that marijuana is not physically addictive, nor does it naturally lead to the use of other illegal drugs. Other studies have found that marijuana lessens some symptoms of glaucoma and discomfort due to cancer, particularly the nausea induced by cancer chemotherapy and radiation treatments. Many people who suffer from these and other chronic diseases report that marijuana provides symptom relief when all other medications fail.
Such findings have provoked a national debate regarding the legalization of marijuana for medicinal use. In 1996 voters in both California and Arizona approved ballot measures exempting physicians and patients from criminal prosecution when marijuana is prescribed for medical purposes in the relief of pain or other symptoms caused by cancer, AIDS, glaucoma, arthritis, and other illnesses and chronic conditions. The Arizona legislature subsequently overturned the measure in that state, but in 1998, voters in Arizona again supported medical marijuana legislation, this time through a ballot initiative, a legislative proposal placed on the ballot by means of public petition. Four other states passed similar ballot initiatives that year, including Washington, Oregon, Alaska, and Nevada. And legislatures in 37 states have passed bills in support of medical marijuana. However, the United States federal government remains opposed to such exemptions to antimarijuana laws. In response to widespread state and grass-roots action, the government warned physicians that they may lose federally sanctioned privileges for writing prescriptions for controlled substances, be barred from participation in federal Medicare and Medicaid programs, and face federal criminal prosecution for prescribing marijuana.
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