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Editor: Jacqueline L. Longe
Date: Sept. 1, 2017
Publisher: Gale, a Cengage Company
Document Type: Topic overview
Length: 2,653 words

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Marijuana Cannabis sativa L., also known as hemp, is a member of the Cannabaceae family. It contains the psychoactive drug delta-9-tetrahydrocannabinol (THC).


Marijuana is a somewhat weedy plant that can grow as high as 18 ft. (5.4 m). The hairy leaves are arranged opposite one another on the erect and branching stem. Leaves are palmate and compound, deeply divided into five to seven narrow, toothed and pointed leaflets. Male and female flowers are small, greenish, and grow on separate plants. Male flowers grow in the leaf axils in elongated clusters. The female flowers grow in spike-like clusters. The resinous blossoms have five sepals and five petals. The male and female blossoms can be distinguished at maturity. The male plant matures first, shedding its pollen and dying after flowering. Female plants die after dropping mature seeds.

Marijuana produces an abundance of quickly germinating seeds. This hardy annual is wind pollinated and has escaped from cultivation to grow wild along roadsides, trails, stream banks, and in wayside places throughout the world. The plant matures within three to five months after the seed has been sown.

The species C. sativa L. has many variations, depending on the soil, temperature, and light conditions, and the origin of the parent seed. These factors also affect the relative amounts of THC and cannabidiol, the active chemicals present in varying amounts in cannabis, and determine if the plant is primarily a fiber type or an intoxicant. Generally the species grown at higher elevations and in hotter climates exude more resin and are more potent intoxicants.


Marijuana has been cultivated for thousands of years. Certain varieties have been used as hemp to make rope; other varieties for their medicinal or hallucinogenic properties. Cannabis was first described for its therapeutic use in the Ming dynasty Chinese pharmacopoeia, the Pen Ts'ao. (A pharmacopoeia is a book containing a list of medicinal drugs and their descriptions of preparation and use.) The Chinese called cannabis a superior herb as early as 2000 B.C.E. and recommended as a treatment for numerous common ailments.

In Ancient Egypt, cannabis was used as a treatment for sore eyes. The herb was used in India in cultural and religious ceremonies and recorded in Sanskrit scriptural texts around 1,400 B.C.E. Cannabis was considered a holy herb and described as a “soother of grief,” “the sky flyer,” and “the poor man's heaven.”

Around 700 B.C.E., the Assyrian people used the herb they called Qunnabu, for incense. The ancient Greeks used cannabis as a remedy for inflammation, earache, and edema. Shortly after 500 B.C.E. the historian and geographer Herodotus recorded that the people known as Scythians used cannabis to produce fine linens. They called the herb kannabis and inhaled the “intoxicating vapor” that resulted when it was burned. By the year 100 B.C.E. the Chinese were using cannabis to make paper.

Cannabis use and cultivation migrated with the movement of various traders and travelers, and knowledge of the herb's value spread throughout the Middle East, Eastern Europe, and Africa. Dioscorides, a surgeon in the Roman Legions under the Emperor Nero (37–68), named the herb Cannabis sativa and recorded numerous medicinal uses. In the second century, the Chinese physician Hoa-Tho, used cannabis in surgical procedures, relying on its analgesic properties. In India, around 600, Sanskrit writers recorded a recipe for “pills of gaiety,” a combination of hemp and sugar. By 1150, Muslims were using cannabis fiber in Europe's first paper production. This use of cannabis as a durable and renewable source of paper fiber continued for the next 750 years.

By the 1300s, government and religious authorities, concerned about the psychoactive effects of consuming the herb, began placing harsh restrictions on its use. The Emir Soudon Shaikhouni of Joneima outlawed cannabis use among the poor. He destroyed the crops and ordered that offenders' teeth be pulled out. In 1484, Pope Innocent VIII outlawed the use of hashish, a concentrated form of cannabis. Cannabis cultivation continued, however, because of its economic value as a fiber-producing plant. A little more than a century later, Elizabeth I of England issued a decree commanding that landowners holding 60 acres or more must grow hemp or pay a fine. Commerce in hemp, which was primarily valued for the strength and versatility of its fibers, was profitable and thriving. Hemp ropes and sails were crossing the sea to North America with the explorers.

By 1621, the British were growing cannabis in Virginia where cultivation of hemp was mandatory. In 1776, the Declaration of Independence was drafted on hemp paper. Both President George Washington and President Thomas Jefferson were advocates of hemp as a valuable cash crop. Jefferson urged farmers to grow the crop in lieu of tobacco. By the 1850s, hemp had become the third largest agricultural crop grown in North America. That year the U.S. Census recorded 8,327 hemp plantations, each with 2,000 or more acres in cultivation. However, the invention of the cotton gin was already bringing many changes, and cotton was becoming a prime and profitable textile fiber. More change came with the introduction of the sulfite and chlorine processes used to turn trees into paper. Restrictions on the personal use of cannabis as a mood-altering, psychoactive herb, were soon to follow.


The 1856 edition of the Encyclopedia Britannica, in its lengthy entry on hemp, noted that the herb “produces inebriation and delirium of decidedly hilarious character, inducing violent laughter, jumping and dancing.” This inebriating effect of marijuana use fueled the controversy and led to restrictions that have surrounded marijuana use throughout history in many cultures and regions of the world. Cannabis use has been criminalized in some parts of the United States since 1915. Utah was the first state to criminalize it, then California and Texas. By 1923, Louisiana, Nevada, Oregon, and Washington had legal restrictions on the herb. New York prohibited cannabis use in 1927. Despite the restrictions, cannabis use was widespread, particularly among the Mexican, Asian, and African American populations.

In the United States in 1937, the federal government passed the Marijuana Tax Act, prohibiting the cultivation and farming of marijuana. The act prohibited industrial and medical use of marijuana and classified the flowering tops as a narcotic. After that, restrictions on the cultivation and use of cannabis continued. Marijuana was categorized as an illegal narcotic, in the company of LSD, heroin, cocaine, and morphine. Despite that, illegal use continued.

In a reversal of the state-by-state progression of criminalizing marijuana that led to the 1937 Marijuana Tax Act, there was a movement to endorse the legalized use of marijuana for medical purposes. By 2017, 29 states in the United States and the District of Columbia had legalized medical or recreational marijuana. A growing body of scientific research and many thousands of years of folk use support the importance of medical marijuana in treatment of a variety of illnesses. The economic value of hemp in the textile, paper, and cordage industries has a long history.

Controversy persists around this herb. The World Health Organization, in a 1998 study, stated that the risks from cannabis use were unlikely to seriously compare to the public health risks of the legal drugs, alcohol, and tobacco. Controversy continues on how addictive marijuana is, given the addiction potential of many prescription drugs used as muscle relaxants, hypnotics, and analgesics. One legitimate concern is the effect of smoking on the lungs. Cannabis smoke carries even more tars and other particulate matter than tobacco smoke.

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Key Terms

A drug or herbal preparation given to relieve nausea and vomiting. Marijuana has antiemetic properties.
The chemical compounds that are the active principles in marijuana.
Swelling of a body tissue due to collection of fluids.
An intense feeling of elation or well being. Many marijuana users experience temporary euphoria.
An eye disorder caused by damage to the optic nerve resulting in vision loss. Glaucoma is usually accompanied by inflammation and increased pressure in the eye (intraocular pressure). There are several types that may develop suddenly or gradually.


The whole cannabis plant, including buds, leaves, seeds, and root, have all been used throughout the long history of this controversial herb. Despite persistent legal restrictions and criminal penalties for illicit use, marijuana continued as of 2017 to be widely used in the United States and throughout the world, both for its mood-altering properties and its medicinal applications. According to the National Survey on Drug Use and Health, in 2015, 22.2 million Americans over age 12 had used marijuana within the past year. In 2017, the World Health Organization (WHO) estimated that 147 million people or 2.5% of the world's population used marijuana.

Causes and symptoms

Marijuana is ingested by smoking the dried herb, which quickly delivers the active ingredients to the blood system. It can also be added to food (often brownies) and eaten. Cannabis contains chemical compounds known as cannabinoids. Different cannabinoids seem to exert different effects on the body after ingestion. Scientific research indicates that these substances have potential therapeutic value for pain relief, control of nausea and vomiting, and appetite stimulation. The primary active agent is THC. This chemical may constitute as much as 12% of the active chemicals in the herb and is said to be responsible for as much as 70%–100% of the euphoric response, or high, experienced when ingesting the herb. The predominance of this mental lightness or euphoria depends on the balance of other active ingredients and the freshness of the herb. THC degrades into a component known as cannabinol, or CBN. This relatively inactive chemical predominates in marijuana that has been stored too long before use. Another chemical component, cannabidiol, known as CBD, has a sedative and mildly analgesic (pain relieving) effect and contributes to lethargy sometimes experienced by marijuana users.

Despite the fact that on the federal level marijuana use remained illegal as of 2017, in the United States there was strong interest in medicinal uses of marijuana. The herb appears to have analgesic, antiemetic, anti-inflammatory, sedative, anticonvulsive, and laxative actions. Clinical studies have demonstrated its effectiveness in relieving nausea and vomiting following chemotherapy treatments for cancer. The herb has also been shown to reduce intra-ocular pressure in the eye, which is beneficial in the treatment for glaucoma. However, marijuana is not more effective in lowering pressure in the eye than legal prescription drugs.

Cannabis has proven anticonvulsive action and may be helpful in treating epilepsy. Marijuana also increases appetite and reduces nausea and has been used with AIDS patients to counter weight loss and wasting that may result from the disease. Several chemical constituents of cannabis displayed antimicrobial action and antibacterial effects in research studies. The components CBC and THC have been shown to destroy and inhibit the growth of streptococci and staphylococci bacteria. In 2007, a Harvard University study found that the active ingredient of marijuana cut lung tumor growth in mice in half.

Because marijuana use is illegal in many places and because diverse plants vary in amounts of active ingredients, there is no standard dosage for medical use. In states that have legalized medical marijuana, the legally permissible amounts for an individual to possess range from 1 oz. (28 g) to 24 oz. (680 g). THC extract is available legally in some countries in capsule form. In the United States this form of THC is available only for clinical experimental purposes.

The PDR for Herbal Medicine reports that the most common effect of marijuana use is psychotropic, as a euphoric state (pronounced gaiety, laughing fits) occurs almost immediately after smoking the herb. Long-term usage leads to a clear increase in tolerance for most of the pharmacological effects. Chronic use results in increased risk of laryngitis, bronchitis, apathy, psychic decline, and disturbances of sexual functions. In addition chronic sinus and fungal infections have been linked to chronic marijuana smoking.

Research has shown that cannabis acts to increase heartbeat by as much as 40 beats per minute. A study reported by the American Heart Association concluded that smoking marijuana can precipitate a heart attack in persons with pre-existing heart conditions. One hour after smoking marijuana, the likelihood of having a heart attack is 4.5 times greater than if the person had not smoked, according to that research. Marijuana also can cause a drop in blood pressure, resulting in dizziness.

Marijuana use during pregnancy has been found to reduce the newborn's birth weight, a possible indication of problems. Pregnant and breastfeeding women should avoid using marijuana. Other research has shown that marijuana decreases male fertility and increases the number of abnormal sperm found in semen.

An additional health concern is the effect that marijuana smoking has on the lungs. Cannabis smoke carries more tars and other particulate matter than tobacco smoke. Long-term use is also associated with an increase in respiratory diseases such as bronchitis.

Studies have shown that motor coordination and driving ability can be impaired for up to eight hours after smoking marijuana. Individuals should avoid driving and using heavy machinery for several hours after using the herb.

More seriously, marijuana has been linked to the onset or worsening of certain psychiatric conditions, including panic disorder, schizophrenia, and depersonalization disorder. Persons diagnosed with or at risk for these conditions should not use marijuana. Chronic marijuana use also interferes with the ability to organize and recall complex information.

Marijuana use may mask the perceived effects of alcohol and cocaine when the drugs are consumed together. Marijuana is said to exert a synergistic effect with other medicinal agents. When used with nitrous oxide it may enhance the nitrous oxide effect.

Marijuana use by individuals taking selective serotonin re-uptake inhibitors (SSRIs, used to treat depression) may develop manic symptoms. Use in individuals taking tricyclic antidepressants can produce delirium and racing heart (tachycardia).

In the United States, marijuana is considered a Class I narcotic, and federal law has restricted its use since 1937. Penalties include fines and imprisonment in some states, but the herb has been decriminalized in others. California, for example, issues cards identifying medical marijuana users and allows them to purchase the drug openly at certain clinics. As of late 2017, 29 states along with the District of Columbia had enacted laws that legalized medical marijuana. In other countries, the legal status of and penalty for using marijuana vary widely.

Illegally purchased marijuana carries the potential to be laced with other toxins and mind-altering drugs. Since marijuana is illegal under federal law, there are no regulations or quality control to establish standardized purity of the herb.


Marijuana use can be diagnosed through a urine drug-screening test. The drug is detectable in urine for 1–5 days after use; however, it may be detected in the urine for as long as 21 days after use. Marijuana use is commonly looked for in pre-employment drug screening.


Many people do not consider recreational marijuana use harmful, especially as the medical community is increasingly recognizing that the drug has medically beneficial qualities. Marijuana use often occurs in conjunction with abuse of alcohol and other drugs. In this situation, treatment of the other drug often takes precedence over treatment for marijuana use. Cognitive-behavioral therapy, in which users learn to recognize, manage and avoid situations most likely to lead to marijuana use, and develop healthy ways to cope with stressful situations can be successful in stopping marijuana use in motivated individuals.


Marijuana use peaks during adolescence and then gradually declines, although there are still many older adults who use marijuana recreationally. Although marijuana is less likely than some other drugs to lead to dependence, heavy users may experience a withdrawal syndrome characterized by anxiety, irritability, chills, and muscle cramps if they stop usage abruptly.


Recreational marijuana use is difficult to prevent, and drug education programs have not been successful in reducing the number of people who experiment with marijuana. As medical use of marijuana became more common, attitudes in the United States have shifted from punishing individuals who possess small amounts of marijuana for personal use, making prevention increasingly difficult.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

Source Citation

Source Citation   (MLA 8th Edition)
Hanrahan, Clare, et al. "Marijuana." The Gale Encyclopedia of Medicine, edited by Jacqueline L. Longe, 5th ed., Gale, 2015. Gale Health and Wellness, Accessed 13 Dec. 2019.

Gale Document Number: GALE|CKMHZB241116484