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Marijuana is derived from the Indian hemp plant, Cannabis sativa, a member of the Cannabaceae family. All types of cannabis strains - both male and female plants - produce THC, the active ingredient that, when smoked or ingested, intoxicates the user. This substance can be detected in every part of the plant, including the stems. The highest concentration of THC, however, is found in the resin, which is most abundant in the flowers of female plants.

Marijuana cannot be easily classified. It is described as a psychogenic (a cannabinoid), a narcotic (although it does not contain opium), and a hallucinogen (the USA government's designation). Each of these definitions, however, is a compromise. Opinion is further divided on whether the drug is a CNS stimulant or a depressant. Controversy also rages over marijuana's medicinal properties, which are alleged and denied fiercely by proponents and detractors, respectively. One fact remains indisputable: marijuana is the most abused illegal drug in the world.


The use of marijuana for both medicinal purposes and relaxation has a history almost as long as its other applications, such as paper or cloth. The world's oldest known pharmacopeia, dated from the third century B.C., recognized the drug's psychoactive qualities and recommended its use as a painkiller, antidepressant, and sedative. Three thousand years later, during the second century A.D., a Chinese surgeon boiled hemp in wine to produce an anaesthetic he called ma fei san.

From China, marijuana spread eastward. In India, its use as a drug began around 1,000 B.C., and it soon became an important part of Hindu religious rituals and meditation. Also, ancient Indian physicians prescribed marijuana for malaria and rheumatism, presumably for its analgesic qualities.

Marijuana soon became popular in the Moslem world, partly because the Islamic faith forbade the use of alcohol. Over the centuries, Arab traders brought cannabis to east Africa, and from there it spread throughout the continent.
By 400 A.D., hemp was being cultivated in Europe and in England.

In the early part of the twentieth century, American soldiers fighting Pancho Villa in Mexico and civilians stationed in Panama during the construction of the canal discovered the intoxicating power of marijuana and brought it back to the States. In the 1930s, the Federal Bureau of Narcotics, forerunner of today's Drug Enforcement Administration (DEA), began a propaganda campaign that portrayed marijuana as a drug that led users to drug addiction, violence, and insanity. At that point, however, cannabis was not only legal, it was an approved medication frequently prescribed by doctors. Marijuana's status changed drastically in 1937, when the Marijuana Tax Act effectively criminalized its use and possession, even for medical reasons.

Chemical Composition

More than 400 chemical compounds have been identified in marijuana. Approximately 60 of these are unique to the cannabis plant and these substances are called cannabinoids. Of the cannabinoids, a group of isomers called tetrahydrocannabinols (THC) are thought to be the most psychoactive. These are ∆1-THC (also called ∆9-THC) and ∆6-THC (also called ∆8-THC). Other cannabinoids include cannabidiolic acid (CBDA), cannabidiol (CBD), and cannabinol (CBN). Their role in marijuana intoxication is not completelly understood. The amount of THC produced depends on the strain of cannabis and on environmental factors such as growth, harvest, and storage conditions.

Because marijuana is a natural product it can also harbor bacteria and fungi, some of which can be harmful if inhaled. Scientists have found bacteria such as Aspergillus, Salmonella, Klebsiella, Enterobacter, and Streptococcus on marijuana samples. This is especially significant for people with compromised immune systems, such as cancer or AIDS patients, many of whom may consider marijuana to counter some of the effects of their disease or treatments.

Not all chemicals found in marijuana occur naturally. When the plant is burned for smoking, hundreds of additional chemicals are produced in the process. Among them are carbon monoxide, cyanide, benzopyrene, and tar. Additionally, any pesticides sprayed on the plant by the grower are present in the smoke, and are inhaled along with the THC.

Types of Cannabis

Indian cannabis. In India, where cannabis has been part of the culture for centuries, three types of cannabis are used.

Bhang is the mildest of India's cannabis concoctions, and is usually eaten as a sweetmeat or consumed as a beverage. It consists of dried cannabis leaves that are ground to a fine paste, mixed with a combination of sugar, spices, and fruit. Because the cannabis is ingested orally, the drug's effects are felt more slowly than when it is smoked. Bhang is the weakest of all cannabis preparations and generally has a low THC concentration.

Ganja, like marijuana, is made from THC-rich cannabis flowers and resin. It is smoked (sometimes mixed with tobacco) in a pipe, a cigarette, or in bidis, small Indian cigars.

Charas is the nearly pure concentrated resin of the cannabis plant. Like ganja, it is smoked, but its THC concentration is far higher.

Marijuana. Marijuana is the dried tobacco-like leaves and flowers of the cannabis plant and is the most common form of the drug in the United States. Marijuana is usually smoked, although it is occasionally baked into foods such as brownies or brewed as tea for drinking.

Hashish. Like charas, hashish is a highly potent, concentrated cannabis resin that has been collected, dried, and pressed into bricks. It is usually ingested by smoking.

Hashish oil. It is extracted from the plant with a chemical solvent such as alcohol or butane. Like hashish, it contains very high concentrations of THC. Hash oil is usually added to tobacco or marijuana cigarettes and is ingested by smoking.

Drug combinations. Marijuana is frequently combined with other drugs, including heroin, cocaine, crack cocaine, LSD, and ecstasy. Taking any combination of drugs is always risky because the effect of each drug is amplified and unpredictable. People on antidepressant medication such as tricyclics who also use marijuana can develop an accelerated heartbeat and high blood pressure, both of which can be dangerous over the long term. Patients who take selective serotonin reuptake inhibitors (SSRIs) such as Paxil and Prozac, and also use marijuana, are at greater risk for severe psychotic episodes. When marijuana is combined with cocaine, the body's drug absorption rate doubles and the stress on the cardiovascular system can rise to dangerous levels since both drugs speed up the heart and raise blood pressure.

Ingestion Methods

Marijuana is usually ingested by smoking, often in joints (loosely rolled cigarettes), a water pipe, or a bong, which filters the smoke through water and is frequently employed when smoking hashish or charas. Marijuana can also be ingested orally, either mixed with other foods or brewed as a tea.

Scope and Severity

Marijuana is by far the most frequently abused illegal drug worldwide. The Office of National Drug Control Policy stated in its 2001 Annual Report that about 80% of Americans abusing illegal drugs used marijuana. The National Institute of Drug Abuse (NIDA), a branch of the National Institutes of Health (NIH), indicated in 2000 that marijuana is also more likely than other illegal drugs to be combined with other controlled substances.

Marijuana is the most abused drug in the European Union. As in the United States, young people were much more likely than other age groups to have used marijuana. Reflecting their national trends, about 15% of the youth surveyed in Finland and Sweden had tried the drug, compared with highs of 28-40% in Denmark, France, Ireland, Netherlands, Spain, and the United Kingdom.

One group that is highly likely to use marijuana, however, cuts across racial, ethnic, and demographic lines: arrestees. The U.S. Department of Justice (DOJ) found that those arrested for crimes were more likely to test positive for marijuana than any other drug.

Mental Effects

Users often experience a mellow sense of well-being and relaxation that makes them feel expansive, creative, and more sensitive to all types of stimuli. Perception of time slows, and ability to gauge distance, depth, and speed accurately is distorted. Users can also spiral downward into anxiety, paranoia, panic attacks, and hallucinations. This effect is more pronounced when larger doses of THC are ingested, such as when hashish or other more concentrated forms of marijuana are used.

Higher doses are also possible when marijuana is eaten rather than smoked; this occurs when more of the drug is ingested before it can be metabolized. Within seconds of entering the bloodstream, the cannabinoids in marijuana bind to special areas in the brain called THC receptors. These regions, located throughout the brain, are heavily concentrated in the hippocampus, which controls learning and memory. This means that one of marijuana's most pronounced effects is its interference with the ability to form short-term memories. A 1996 study published in the Journal of the American Medical Association showed that heavy marijuana users, defined as those who ingest the drug on a daily or nearly daily basis, scored significantly lower on learning and other tests. This most likely occurs because THC changes the way the brain processes new information; THC stifles neural activity in the hippocampus by suppressing acetylcholine release. Long-term use can cause changes in users' brains that are similar to those caused by other controlled substances.

Physiological Effects

While it is true that most people smoke marijuana precisely for its mental effects, they may not be aware of the physical changes that accompany the high. One of the drug's first effects is to raise the heart rate and blood pressure. The eyes become bloodshot and the pupils dilate; the mouth and throat also become dry. The appetite is stimulated, and users often become unusually hungry.

At the same time, the cannabinoids in marijuana, already at work in the hippocampus, bind to THC receptors in other parts of the brain, including the basal ganglia, which govern the body's involuntary muscles, and the cerebellum, which controls coordination and sense of balance. These changes relax muscles all over the body, slowing reaction time and impairing the body's ability to move efficiently. When the high wears off, fatigue and torpor replace the creativity and hyperawareness users may experience initially.


As the drug is broken down by the body, fat-soluble THC metabolites accumulate in the liver and other organs. Thirty percent of any one dose of THC is still in the body a week later, and smaller but still-detectable amounts are present two weeks after that. The more often marijuana is used, the greater the buildup in the body; heavy users' urine may show traces of the drug more than a month after the last dose.

Harmful Side Effects

Despite a popular myth that cannabis use is harmless, marijuana smoke, like cigarette smoke, contains cyanide, as well as higher levels of benzopyrene and carbon monoxide. Marijuana joints the same size as a cigarette produce five times the carbon monoxide in subjects' blood. Smoking marijuana produces three to four times the tar of tobacco, and more of it stays in the lungs. Because marijuana smoke is inhaled more deeply and held far longer in the lungs than tobacco smoke, damage to the delicate pleural tissues is as or more pronounced. Some researchers equate one joint to five cigarettes; others contend that three to four joints are as damaging as a pack of cigarettes.

Women who smoke marijuana during pregnancy may have low birth-weight babies who are at risk for developmental difficulties and are more susceptible to disease. Like other drugs, THC also crosses the placental barrier and affects the embryo as it grows; some studies indicate that this may increase a baby's risk of developing leukemia. THC also passes into breast milk, where research has shown that it can affect a child's motor development. Toddlers whose parents smoke marijuana have been found to be angrier and to have more behavioral problems than children whose parents do not use marijuana.

Long-term Health Effects
Marijuana smokers are at higher risk than nonusers for chronic lung diseases such as bronchitis, asthma, lung infections, and emphysema. Research also indicates that heavy marijuana use can lead to the DNA damage and cellular changes that produce lung cancer; these changes appeared to occur in marijuana smokers at anearlier age than in tobacco smokers. Cancers of the head and neck are also more common in marijuana smokers. People who smoke both marijuana and tobacco are at an even higher risk of serious disease. In men, heavy long-term marijuana use can lead to lowered sperm counts and even impotence. It can also cause a hormone imbalance that leads to gynecomastia, the development of feminine breasts. Women who abuse marijuana may experience menstrual cycles that are off balance.

Reactions with Other Drugs or Substances

As noted above, marijuana is frequently combined with other drugs. Sometimes joints or blunts are laced with PCP, crack, heroin, or other controlled substances; at other times, marijuana is used along with drugs like alcohol or cocaine. Any such drug combination amplifies the effect of both substances, sometimes dangerously. The National Highway Transportation Safety Administration showed that a combined dose of alcohol and marijuana was far more debilitating than either one alone. Using marijuana with LSD or other hallucinogens increases the psychotropic effect, sometimes adversely. Combining marijuana with cocaine increases the already measurable stress that each drug independently exerts on the cardiovascular system.

Treatment and Rehabilitation

Experts are divided on whether or not heavy, long-term marijuana use causes the same kind of addiction that opium or crack does. Evidence shows that daily marijuana use over time can lead to withdrawal symptoms such as aggression, irritability, and stomach pains; these are hallmarks of addiction. Also, long-term use can cause some of the same destructive brain changes as those found in other types of drug addictions. Studies in 1997 showed that THC causes a dopamine release in the brains of rats equivalent to that seen with heroin. It is estimated that more than 120,000 people seek treatment for marijuana dependence each year, indicating that at the very least marijuana use can become an overwhelming compulsion that is extremely difficult to break. After alcohol and nicotine, marijuana is the drug on which more people become dependent than any other. Dependence is greatly increased by the additional abuse of another drug (particularly alcohol) and the presence of psychiatric disorders.

In addition, young people seem especially vulnerable to marijuana dependence. In a 1998 study, out of a group of 229 adolescents already dependent on one substance (usually alcohol), 83% ofthose who tried marijuana six or more times became dependent on it as well. Most of these young people also showed symptoms of antisocial/behavioral problems.

The first step in treating marijuana dependence is detoxification. This is a series of medical and nutritional therapies designed to help the patient through withdrawal symptoms by eliminating drugs from the body. Once detox has been accomplished, psychological counseling
and education programs help users face life without depending on drugs. However, success is not guaranteed. Users relapse frequently, sometimes merely shifting their dependence from marijuana to alcohol or another drug.


Heavy users with an average daily intake of three to five joints are likely to have problems in all aspects of their lives, both at home and at work, ranging from strained familial relationships to job loss. They are also more likely to exhibit neurotic or even psychotic behavior. Research shows that marijuana users, especially heavy users, end up in the hospital more frequently than nonusers, often from injuries. One of the worst aspects of heavy marijuana use may be what researchers call the "amotivational syndrome" that robs people of their ambition, drive, and energy. A 2000 study showed that teenagers who use marijuana drop out of high school at more than twice the rate of nonusers; those who also abuse other drugs have even higher dropout rates.

Teenagers who face legal consequences because of their marijuana use may jeopardize their chance of getting financial aid for college. Applications for students requesting federal college loans ask whether or not they have ever been convicted on state or federal drug charges. An affirmative answer - or none at all - will hold up the application and may well cause the application to be rejected.
Marijuana users will find that many employers weed out substance abusers, because they are much more likely to be absent or have on-the-job accidents. In 1996, about a third of all potential hires were screened for drug use. At major corporations, the figure was 81%, and in the top-ranked Fortune 200 companies, it rose to 98%. Standards at many federal agencies are even more stringent: the Federal Bureau of Investigation (FBI) will disqualify applicants who had used marijuana within the past three years or a total of 15 times altogether.

Legal History

Until the twentieth century, cannabis was a legal product in every state. It was an accepted medication for a variety of conditions, and a frequent ingredient in patent medicines. In 1906, the Pure Food and Drug Act forbade "the manufacture, sale, or transportation of adulterated or misbranded or poisonous or deleterious foods, drugs, medicines, and liquors," including those containing cannabis. The law put most patent medicine manufacturers out of business.

By 1931, 29 states had outlawed marijuana. In 1937, Congress passed the Marijuana Tax Act, which effectively criminalized marijuana possession anywhere in the United States, even for ostensibly medicinal use. In the 1950s, federal penalties increased further: a firsttime marijuana conviction could mean as much as 10 years in jail and up to $20,000 in fines.

Beginning in the 1960s, however, the perception of marijuana as a relatively harmless drug gained popular acceptance, particularly among the young. In 1970, Congress lifted many mandatory sentences for drug crimes. The Comprehensive Drug Abuse Prevention and Control Act allowed possession of small amounts of marijuana, although the drug remained a controlled substance, and large-scale trafficking was heavily penalized.

After years of relative tolerance, however, mandatory sentences for drug-related crimes were reinstated in 1986 by the Anti-Drug Abuse Act, which tied criminal penalties to the quantities of drugs involved. Later amendments to the act further tightened the judicial noose with a "three-strikes" clause and capital punishment for high-level criminals. Marijuana trafficking is vigorously prosecuted in the United States, with the FBI reporting that nearly half of its 1.5 million drug arrests in 2000 were for marijuana. More than 87% of these arrests were for possession. First-offense convictions for possession of less than 110 lbs (50 kg) of marijuana are punishable by up to five years in prison and fines of up to $250,000 for an individual. Those convicted of possessing more than 2,205 lbs (1,000 kg) of marijuana face up to life in prison and fines of up to $4,000,000.


1. Blachford S.L. and Krapp K. eds. Drugs and Controlled Substances Information for Students, Detroit:Thomson Gale, 2003.
2. Emmett D. and Nice G. Understanding Street Drugs. 2d ed. London: Jessica Kingsley Publishers, 2006.
3.NIDA InfoFacts: Marijuana
4.Fact Sheet Marijuana ADA

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