Marijuana is the most commonly abused illicit drug in the United States. A dry, shredded green/brown mix of flowers, stems, seeds, and leaves of the plant Cannabis sativa, it usually is smoked as a cigarette (joint, nail), or in a pipe (bong). It also is smoked in blunts, which are cigars that have been emptied of tobacco and refilled with marijuana, often in combination with another drug. It might also be mixed in food or brewed as a tea. As a more concentrated, resinous form it is called hashish and, as a sticky black liquid, hash oil. Marijuana smoke has a pungent and distinctive, usually sweet-and-sour odor.

The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). The membranes of certain nerve cells in the brain contain protein receptors that bind to THC. Once securely in place, THC kicks off a series of cellular reactions that ultimately lead to the high that users experience when they smoke marijuana.


Grass, pot, weed, bud, Mary Jane, dope, indo, hydro


When marijuana is smoked, its effects begin immediately after the drug enters the brain and last from 1 to 3 hours. If marijuana is consumed in food or drink, the short-term effects begin more slowly, usually in 1/2 to 1 hour, and last longer, for as long as 4 hours. Smoking marijuana deposits several times more THC into the blood than does eating or drinking the drug.

Within a few minutes after inhaling marijuana smoke, an individual’s heart begins beating more rapidly, the bronchial passages relax and become enlarged, and blood vessels in the eyes expand, making the eyes look red. The heart rate, normally 70 to 80 beats per minute, may increase by 20 to 50 beats per minute or, in some cases, even double. This effect can be greater if other drugs are taken with marijuana.

As THC enters the brain, it causes a user to feel euphoric— or “high”—by acting in the brain’s reward system, areas of the brain that respond to stimuli such as food and drink as well as most drugs of abuse. THC activates the reward system in the same way that nearly all drugs of abuse do, by stimulating brain cells to release the chemical dopamine.

A marijuana user may experience pleasant sensations, colors and sounds may seem more intense, and time appears to pass very slowly. The user’s mouth feels dry, and he or she may suddenly become very hungry and thirsty. His or her hands may tremble and grow cold. The euphoria passes after awhile, and then the user may feel sleepy or depressed. Occasionally, marijuana use produces anxiety, fear, distrust, or panic.

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Someone who smokes marijuana regularly may have many of the same respiratory problems that tobacco smokers do, such as daily cough and phlegm production, more frequent acute chest illnesses, a heightened risk of lung infections, and a greater tendency toward obstructed airways. Cancer of the respiratory tract and lungs may also be promoted by marijuana smoke. Marijuana has the potential to promote cancer of the lungs and other parts of the respiratory tract because marijuana smoke contains 50 percent to 70 percent more carcinogenic hydrocarbons than does tobacco smoke.

Marijuana's damage to short-term memory seems to occur because THC alters the way in which information is processed by the hippocampus, a brain area responsible for memory formation. In one study, researchers compared marijuana smoking and nonsmoking 12th-graders' scores on standardized tests of verbal and mathematical skills. Although all of the students had scored equally well in 4th grade, those who were heavy marijuana smokers, i.e., those who used marijuana seven or more times per week, scored significantly lower in 12th grade than nonsmokers. Another study of 129 college students found that among heavy users of marijuana critical skills related to attention, memory, and learning were significantly impaired, even after they had not used the drug for at least 24 hours.

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Overall marijuana production in Mexico--the principal source of foreign-produced marijuana to U.S. drug markets appears to be increasing. Mexico marijuana production estimates indicate that production in Mexico was relatively low from 2000 through 2002 during a period of drought, increased sharply in 2003 as weather improved, and receded slightly in 2004. Moreover, anecdotal reporting and cannabis eradication and marijuana seizure data all indicate that marijuana production in Canada has recently increased, perhaps significantly. Domestic marijuana production also appears to be increasing, according to law enforcement reporting that reveals a significant increase in eradication of domestic marijuana grow sites in 2005. Domestic Cannabis Eradication/Suppression Program (DCE/SP) data indicate that domestic cannabis eradication--occurring primarily in California, Kentucky, Tennessee, Hawaii, and Washington, often on public lands including Forest Service lands increased steadily from 2000 through 2003, decreased in 2004, and increased sharply to its highest recorded level in 2005.

Most of the foreign-produced marijuana available in the United States is smuggled into the country from Mexico via the U.S.-Mexico border by Mexican DTOs and criminal groups; however, a sharp rise in marijuana smuggling from Canada via the U.S.-Canada border by Asian criminal groups has increased the domestic availability of marijuana produced in Canada.

Mexican criminal groups control most wholesale marijuana distribution throughout the United States; however, Asian criminal groups appear to be increasing their position as wholesale distributors of Canada-produced marijuana. According to law enforcement reporting, Mexican DTOs and criminal groups control most wholesale marijuana distribution in the Great Lakes, Pacific, Southeast, Southwest, and West Central Regions and control much of the wholesale marijuana distribution in the Northeast Region. Although Asian criminal groups are not the predominant wholesale marijuana distributors in any region, these groups, particularly Chinese and Vietnamese groups, now are widely identified in law enforcement reporting as the principal suppliers of high potency, Canada-produced marijuana throughout the country.

The influence of Asian criminal groups in high potency marijuana distribution is likely to increase in the near term. Law enforcement reporting indicates that these groups are increasingly gaining control over much of the high potency marijuana production and distribution in Canada and now appear to be extending their influence in the United States. In fact, law enforcement reporting indicates that the influence of Asian organizations in drug trafficking--particularly the trafficking of high potency marijuana--in the United States is now more significant than that of Russian-Israeli, Jamaican, or Puerto Rican criminal groups.

Marijuana distribution is widespread throughout the country, as evidenced by the presence of 14 principal distribution centers for the drug, one or more of which are located in nearly every region of the country. Much of the midlevel and retail distribution of marijuana in these and other cities is controlled by African American, Asian, and Hispanic street gangs; however, independent dealers control most midlevel and retail marijuana distribution in smaller communities and rural areas. In fact, independent dealers are likely to retain control of distribution in smaller communities because they often distribute locally produced marijuana rather than foreign-produced marijuana.

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Among students surveyed as part of the 2005 Monitoring the Future study, 16.5% of eighth graders, 34.1% of tenth graders, and 44.8% of twelfth graders reported lifetime use of marijuana. In 2004, these percentages were 16.3%, 35.1%, and 45.7%, respectively.

Approximately 74% of eighth graders, 65.5% of tenth graders, and 58% of twelfth graders surveyed in 2005 reported that smoking marijuana regularly was a "great risk."

The Youth Risk Behavior Surveillance (YRBS) study by the Centers for Disease Control and Prevention (CDC) surveys high school students on several risk factors including drug and alcohol use. Results of the 2005 survey indicate that 38.4% of high school students reported using marijuana at some point in their lifetimes. Additional YRBS results indicate that 20.2% of students surveyed in 2005 reported current (past month) use of marijuana.

Between 2001 and 2005, marijuana use dropped in all three categories: lifetime (13%), past year (15%) and 30-day use (19%). Current marijuana use decreased 28% among 8th graders (from 9.2% to 6.6%), and 23% among 10th graders (from 19.8% to 15.2%)