Home > Encyclopedia of Drugs, Alcohol, and Addictive Behavior > Marijuana

BOTANY

Hemp grows easily throughout the tropics, sub-tropics, and temperate regions, varying from a few feet to 15 feet (4.6 m) in height. Once established, it reseeds itself and spreads to neighboring areas; when birds eat the seeds, the defecated seeds may be scattered over considerable distances and produce new plants.

Two genetic strains of hemp are recognized: one produces plants excellent for fiber with very little drug material; the other produces plants with weak fibers but much drug content (TETRAHYDROCANNABINOL, THC). To harvest the drug-laden plant, it is simply cut down and usually chopped into small pieces with all parts included. These clippings resemble lawn cuttings, so one of the slang terms is "grass." The major use of this form in the United States is for illegal marijuana cigarettes, often called reefers.

Since the early 1900s, marijuana has been considered the one drug that might introduce the susceptible to hard drugs, drug abuse, and drug dealing. In the United States until 1937, Cannabis had been used in medical practice for a number of conditions but marijuana use for its euphoric effect was relatively uncommon. By 1937, forty-six of the then forty-eight states had laws against the use of marijuana, and its use had already been made a criminal offense under federal law. Until the 1960s, it was smoked largely by African Americans and Hispanics in the United States but was generally shunned by the white majority. During the social and political protests of the 1960s, a change in attitudes allowed widespread but illegal marijuana use into all levels of society, along with an increase in the use of several other illegal drugs and a boom in the drug trade that continued into the 1990s.

HISTORY

Various historical allusions to medicinal plants suggest that Cannabis was known and used for several thousand years. The earliest references to the plant are in ancient Chinese and Indian writings. From India, the use of Cannabis spread to Persia, Assyria, and the rest of the Near East. The Arabs adopted and spread it through North Africa as they conquered those lands for Islam from the seventh to the fifteenth centuries. Islam forbids the use of ALCOHOL, but not explicitly Cannabis (since it was adopted after the laws established by the Prophet Muhammad, who lived from about 570 to about 632 A.D.). In Arabic, it is called HASHISH, meaning grass. After the Arabs crossed the Strait of Gibraltar into the Iberian peninsula in 711, they ruled there until 1492. Portugal and Spain did not generally adopt its use. The Spanish conquistadors, however, introduced Cannabis into the New World, where it was readily adopted by African slaves, who were already familiar with it because of Arab trade and the spread of Islam into their continent.

CHEMISTRY

Like most plants, Cannabis contains many substances, perhaps two hundred or more. Those that relate most to the drug effects are a group of chemically similar compounds called cannabinoids. Of these, the most important and plentiful are cannabidiol (CBD), tetrahydrocannabinol (THC), and cannabinol (CBN). The biosynthetic pathway in the plant (that is, the step-by-step sequence in which the plant produces substances) goes from CBD to THC to CBN. Thus it is possible to identify the maturity of the plant by the relative content of these three cannabinoids. Immature plants show a preponderance of CBD; old plants may contain solely CBN; plants that are at their peak contain all cannabinoids, but mostly THC, which is the agent that produces the mind-altering effect. Some strains of plants contain variants on the THC structure, which usually have somewhat less drug effect than those with THC. Although some users contend that marijuana has different effects from those of isolated THC, most evidence indicates that virtually all of the mind-altering effects of marijuana are attributable to the THC content.

The THC content may vary greatly, depending on the genetic strain of the plant, the part of the plant involved (for example, the leaves or the flowers), and the maturity of the plant. The THC content of plants used for hemp production, such as those that grow wild in the U.S. Midwest, may be negligible to zero; marijuana produced from plants known for high drug content, such as sensemilla, may contain 2 to 3 percent THC. Manicured plants, from which the leaves are carefully separated and only the new leaves used for drug effect, may contain 3 to 4 percent THC. Hashish, which represents the ultimate in manicuring, generally contains 4 to 8 percent THC.

THC is sensitive to exposure to air and light. Thus, marijuana that is not protected from such exposure undergoes gradual degradation until the drug content is gone. When protected from air and light, marijuana may retain its activity for many months.

EPIDEMIOLOGY

Marijuana may rank behind only CAFFEINE, alcohol, and NICOTINE as the most widely used drug in the world. It is estimated that between 200 and 300 million people use this material in one way or another. In the United States alone, probably some 20 to 30 million people have used the drug, although the number of regular users is probably far less, but still a few million.

In the United States, marijuana is a drug preferred by young people; the rate of marijuana use is therefore followed among schoolchildren to estimate changing trends. Survey responses of highschool students, concerning marijuana, show very wide variations. Overall, 3 to 17 percent (median 12%) reported at least a single use of marijuana during the preceding thirty days. Such use is relatively low compared with that of smoking at least one cigarette, 9 to 37 percent (median 31%), or having at least one drink of alcohol, 28 to 64 percent (median 54%). Thus, it would appear that marijuana is not nearly as widely used as two of our three national drugs. Although this data indicates a trend toward decreased use of and greater concern about marijuana compared with nicotine and alcohol, this pattern has not held long enough to establish a true trend; it may be simply a minor blip.

A number of factors seem to contribute to use of marijuana among young people. Being male, using cigarettes and alcohol, and becoming delinquent are predisposing factors. Coming from a broken home and performing poorly in school are also predictive factors. Among adolescents in Australia and New Zealand, use of stimulants, HALLUCINOGENS, NARCOTICS, and SEDATIVES was virtually limited to those young people who used marijuana. Overall, it appears that school factors are less predictive of Cannabis use than are other social factors.

PSYCHOPHARMACOLOGY

Marijuana has a wide range of pharmacologic effects that suggest actions like those of stimulants such as the AMPHETAMINES, hallucinogens such as LSD, and depressants such as alcohol, SEDATIVES, atropine, or MORPHINE. Thus, marijuana does not fit any single traditional pharmacologic classification, and, hence, must be considered as a separate class.

The experienced smoker of marijuana is usually aware of a drug effect after two or three inhalations. As smoking continues, the effects increase, reaching a maximum about twenty minutes after the smoke has been finished. Most effects of the drug have usually vanished after three hours, by which time tests show that concentrations of THC in the body's plasma are low. Peak effects after eating marijuana may be delayed for three to four hours, but may then last for six to eight hours.

The early stage is one of being high, characterized by euphoria, uncontrollable laughter, alteration of one's sense of time, depersonalization, and sharpened vision. Later, the user becomes relaxed and experiences introspective and dreamlike states, if not actual sleep. Thinking or concentrating becomes difficult, although by force of will the person can concentrate to some extent.

Two characteristic signs of Cannabis intoxication are increased pulse rate and reddening of the conjunctiva (the whites of the eyes). The latter correlates well with the presence of detectable concentrations of THC in the plasma. Pupil size is not changed. The blood pressure may fall, especially in the upright position (orthostatic hypotension). An antiemetic (decrease in sense of nausea) effect may be present, and muscle weakness, tremors, unsteadiness, and increased deep-tendon reflexes (such as the knee jerk) may also be noted.

Virtually any performance test shows impairment if the doses are large enough and the test is difficult enough, although no distinctive biochemical changes have been found in human beings.

TOLERANCE to Cannabis has been demonstrated in virtually every animal species that has been tested. It is apparent in human beings only among heavy long-term users. Different degrees of tolerance develop for different effects of the drug, with tolerance for the tachycardiac effect (increased pulse rate) developing fairly rapidly. A mild WITHDRAWAL syndrome has been noted following very high doses.

HEALTH CONSEQUENCES

The ambiguity surrounding the health hazards of Cannabis may be attributed to a number of factors besides those that ordinarily prevail. First, from animal studies, it has been difficult to prove or disprove health hazards in human beings. Second, Cannabis is still used mainly by young persons in the best of health. Third, Cannabis is often used in combination with tobacco and alcohol, among licit drugs, as well as with a variety of other illicit drugs. Finally, the whole issue of Cannabis use is so laden with emotion that serious investigations of the health hazards of the drug have been colored by the prejudices of the experimenter, either for or against the drug as a potential hazard or benefit to health.

Psychiatric Consequences.

Cannabis may directly produce an acute panic reaction, a toxic delirium, an acute paranoid state, or acute mania. Whether it can directly evoke depressive or schizophrenic states, or whether it can lead to sociopathy or even to the so-called AMOTIVATIONAL SYNDROME is much less certain.

That Cannabis use may make schizophrenia already present even worse is beyond any question. Such worsening followed acutely after use of Cannabis by schizophrenics, despite continued maintenance of antipsychotic drugs, and other adverse reactions were encountered among seventy patients in Sweden—anxiety reactions, flashbacks, dysphoric reactions, and abstinence syndromes.

Whether chronic use of Cannabis changes the basic personality of users so that they become less impelled to work and to strive for success has been a vexing question. As with other questions concerning Cannabis use, it is difficult to separate consequences from possible causes.

Automobile Driving.

If marijuana were to become an accepted social drug, it would be important to know its effects on driving ability. Fully 50 percent of the fatal auto accidents in the United States are associated with alcohol, another social drug. Neither experimental nor epidemiological approaches to the marijuana question have yet provided definitive answers.

Cardiovascular Problems.

For persons with heart disease caused by hardening of the coronary arteries or by congestive heart failure, the effects of Cannabis smoking would be harmful: tachycardia, orthostatic hypotension, and increased concentrations of carbon monoxide in the blood.

Clearly, smoking of any kind is bad for patients with angina, but the greater effect of Cannabis as compared with tobacco in increasing heart rate makes this drug especially bad for such patients. Fortunately, thus far, few angina patients have been devotees of Cannabis.

Lung Problems.

Virtually all users of Cannabis in North America take the drug by smoking. As inhaling any foreign material into the lung may have adverse consequences, well proven in the case of tobacco, this mode of administration of Cannabis might also be suspect. A formal study has shown that very heavy marijuana smoking for six to eight weeks caused mild but significant airway obstruction.

The issue of damage to lungs from Cannabis is somewhat unclear because many Cannabis users also use tobacco. As yet, it is far easier to find pulmonary cripples from the abuse of tobacco than it is to find any evidence of clinically important weakness of the lungs caused by smoking Cannabis.

Endocrine and Metabolic Effects.

A review of literature on this subject concluded that sperm production was decreased, but without evidence of infertility. Ovulation was inhibited as luteinizing hormone, which stimulates ovulation, was decreased.

Immunity.

A number of test-tube studies, using both human and animal material, suggest that cell-mediated immunity (the capacity of white blood cells to fight invading bacteria, viruses, or cancer cells) may be decreased after exposure to Cannabis. Clinically, one might assume that sustained impairment of cell-mediated immunity might lead to increased opportunistic infections or to increased prevalence of cancer, as seen in the current epidemic of ACQUIRED IMMUNODEFICIENCY SYNDROME (AIDS). No such clinical evidence has been discovered.

THERAPEUTIC USES

For many centuries, Cannabis was used as a treatment, but only during the nineteenth century did a particularly lively interest develop for exploiting its healing powers. Cannabis was then reported to be effective in treating tetanus, convulsive disorders, neuralgia, migraine, menstrual problems, psychoses following childbirth, insomnia in the aged, depression, and gonorrhea, as well as in helping cure addiction to opium or to chloral hydrate. In addition, it was used to stimulate appetite and to relieve the pain and anxiety of patients terminally ill with cancer. Few of these claims have even been properly tested in clinical studies.

Antiemetic for Patients in Cancer Chemo-therapy.

An antiemetic is a substance that suppresses vomiting. CANCER chemotherapy, especially with the agent cisplatin, produces severe nausea and vomiting, which is extremely difficult to treat with ordinary antiemetic drugs, such as prochlorperazine. This complication is so severe that many patients forgo effective cancer chemotherapy. The antiemetic effects of Cannabis had been suggested as early as 1972. In that year, a synthetic drug similar to THC, nabilone, was developed. It has been tested extensively for antiemetic activity. A crossover study comparing nabilone with prochlorperazine revealed significantly better results (that is, less nausea and vomiting) following nabilone therapy, although side effects from nabilone were also common.

The potential role of THC as an antiemetic may have become irrelevant because of recent developments. Metoclopramide, a newly developed antiemetic unrelated to the cannabinoids, has been found to be effective when given in high intravenous doses. Lorazepam, dexamethasone, and ondansetron are also useful as antiemetic agents when given by injection. These drugs are often used in various combinations, which meet most requirements. Thus, THC may be superseded even before it has had widespread clinical trial.

Glaucoma.

The disease glaucoma causes pressure in the eyeball to increase greatly. If untreated, it can lead to blindness. Discovery of the ability of Cannabis to lower intraocular (inside the eyeball) pressure was more or less a matter of chance. This pressure was measured as part of a multifaceted study of the effects of chronic smoking of large amounts of Cannabis: it decreased as much as 45 percent in nine of eleven subjects, thirty minutes after smoking.

This exploitation of cannabinoids for treatment of glaucoma will require much further developmental work to ascertain which cannabinoid will be lastingly effective and well tolerated topically.

Miscellaneous Uses.

Cannabinoids have been found to have analgesic (pain-relieving) activity, and efforts are being made to synthesize new compounds that separate this action from the others. They have also been used for relaxing muscles, for treating bronchial asthma, and for stopping convulsions. Thus far, none of these additional potential therapeutic uses has been fully established.

TREATMENT OF MARIJUANA USE

In general, marijuana users, even those whose use is heavy, do not feel compelled to seek treatment unless such use is complicated by other drugs, such as COCAINE or alcohol. In this case, treatment efforts are usually directed toward the complicating drug. Thus, treatment programs directed specifically at marijuana use are rare. A TWELVE-S TEP approach, similar to that for alcohol, has been proposed, but its feasibility and its efficacy have not been tested.

GATEWAY EFFECT

Since about 1950 (but not much prior to that time) in the United States, smoking of marijuana has been linked statistically to the use of other illegal drugs, such as heroin and cocaine. Most observers have concluded that the link is sociological rather than biological, and that the use of marijuana is a marker for individuals who are more prone to seek new experiences even when these violate social norms and local laws. Further, the process of obtaining illegal marijuana increases the likelihood of contact with dealers and other individuals who have access to drugs such as HEROIN. Consequently, marijuana has been referred to as a "gateway" drug, one whose use often leads to the use of other illegal drugs. Some programs are aimed at preventing even experimentation with marijuana—not only for whatever inherent benefits this approach may have, but also in the hope that in doing so the movement to other more potentially lethal drugs will be prevented.

LEGAL STATUS

Despite its widespread use, marijuana has not yet been admitted to the company of accepted social drugs such as alcohol and nicotine. Laws remain that prescribe penalties for its possession, use, and sale. In some jurisdictions, possession and use of small amounts of the drug is a civil crime punishable only by a small fine. Despite the liberalization of the law in these areas, they have not been overrun with eager marijuana users. Perhaps the reason is that in most other jurisdictions, laws against its use are rarely enforced. Enforcement can be capricious, however, when employed in situations in which more serious crimes cannot be adequately documented.

A new drug application was approved for THC (Marinol) to be used therapeutically for control of the nausea and vomiting associated with cancer chemotherapy. Thus, THC was moved from Schedule 1 of controlled substances (no medical use) to Schedule 2 (medical use despite potential for abuse). Nabilone, the synthetic drug similar to THC, used for the same purpose, also has this status.

Thus far, no attempt has been made to establish legal limits on the amounts of THC in the blood that might be construed as impairing automobile driving. No doubt the issue has not yet appeared to be of enough gravity, since marijuana contributes little to the danger of driving as compared with alcohol.

(SEE ALSO: Adolescents and Drug Use; Cannabis Sativa; Complications; ; Driving, Alcohol, and Drugs; High School Senior Survey; Marihuana Commission; Yippies)

LEO E. HOLLISTER

REVISED BY JAMES T. MCDONOUGH, JR.