Multiple: Marijuana Use

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Multiple: Marijuana Use

Causes and Symptoms
The Future
For more information


Marijuana is a mixture of the dried leaves, stems, seeds, and buds of the hemp plant, Cannabis sativa. Dry marijuana is greenish or grey in color. Hashish, which contains the same mood-altering chemicals as marijuana, is a concentrated resin made from the flowering tops of hemp plants.


Marijuana is used in medicine (see sidebar) but is better known as a drug used for pleasure or to relieve stress and anxiety. It is the most widely used illegal drug worldwide. Marijuana is usually smoked in the form of a cigarette (“joint” or “reefer”), a cigar (“blunt”), or through a water pipe known as a bong. It can also be brewed as a tea or added to cookies, cakes, and other recipes. Hashish can be smoked, used as a food ingredient, or eaten alone.

The compound contained in marijuana that produces most of the plant's mood-altering effects is called THC, which is an abbreviation of its chemical name (delta-9-tetrahydrocannabinol). THC affects the parts of the brain that control memory, logical thought, muscle coordination, pleasure, the ability to concentrate, sense perception, and awareness of time. The concentration of THC in marijuana varies from 1–5 percent in most samples to as high as 15–17 percent in some specially cultivated varieties of the hemp plant. Hashish contains from 5–15 percent THC, and hashish oil contains 20 percent.


Marijuana is used as a recreational drug by people in all age groups. However, it is primarily a drug used by adolescents and young adults. Over ninety-four million Americans (40 percent) over the age of twelve have tried marijuana at least once, according to the 2003 National Survey on Drug Use and Health (NSDUH). Habitual use of the drug, however, goes up and down. In the late 1970s, more than 60 percent of high school seniors tried marijuana at least once, but this figure dropped to 33 percent by 1992. The percentage rose to 50 percent by 2002, where it has remained.

About 17 percent of young adults between the ages of eighteen and twenty-five and about 4.1 percent of adults over twenty-six reported using marijuana once a month in 2005. The rates of marijuana use varied among different racial groups in the United States, with Asians reporting the lowest rate (3.1 percent) and Native Americans the highest (12.8 percent). The rates for African Americans, Caucasians, and Hispanics were 9.7 percent, 8.1 percent, and 7.1 percent respectively.

Men are more likely (10.2 percent) than women (6 percent) to use marijuana on a regular basis.

Marijuana is responsible for more than 120,000 visits to hospital emergency rooms in the United States each year. Fifteen percent of these patients are between the ages of twelve and seventeen, and two-thirds of them are male.

Causes and Symptoms

The THC contained in marijuana reaches the brain via the bloodstream, either from the digestive tract or from the lungs. The process is slower if the marijuana is taken by mouth than if it is smoked. It takes about half an hour for a person to feel the effects of marijuana contained in food or brewed as tea. Smoked marijuana reaches the brain in five to ten minutes. Once in the brain, THC attaches itself to nerve cells in the parts of the brain that control appetite, temperature regulation, memory, motor coordination, learning, short-term memory, sight, taste, hearing, and the ability to concentrate and think clearly.

Each intake of marijuana smoke is called a hit. If the marijuana is very strong, it may take only two or three hits for users to feel the effects of the drug. The psychological effects of marijuana last between six and twelve hours. However, the effects of the drug on motor coordination, short-term memory, and the ability to concentrate may last for as long as two days.

The effects of marijuana are not the same for all users. Depending on the strength of the marijuana, the person's emotional state at the time,

Medical Marijuana

Marijuana has been used to treat pain and insomnia for at least 4,000 years, judging from ancient Indian and Egyptian medical texts. Marijuana use for medical purposes today, however, is controversial. It is difficult to isolate the chemicals in marijuana that relieve pain, bring sleep, and prevent vomiting from those that lead to addiction or psychotic episodes. A synthetic form of THC, the main chemical in marijuana, is used in dronabinol, a medication given to AIDS and cancer patients to relieve vomiting and increase appetite. THC helps relieve muscle cramps and spasms, as well as some symptoms of multiple sclerosis. THC can lower the fluid pressure inside the eyeball, leading some doctors to find it useful in treating glaucoma.

Several major difficulties exist in measuring the effectiveness of dried marijuana as a treatment for pain and nausea. The potency (strength) of marijuana varies considerably from sample to sample. The average sample of marijuana in the 1960s contained about 0.4 percent THC, whereas many samples in the 1990s contained between 2 and 4 percent THC. In the early 2000s, some people have produced marijuana that contains 15 or 17 percent THC. This wide variation complicates clinical studies of marijuana.

Using marijuana to treat AIDS and cancer patients is complicated because marijuana smoke

irritates the lungs of some patients. Also, doctors have yet to research chemicals others than THC that are contained in marijuana. It is possible that some of these compounds could be harmful to patients already weakened by AIDS, cancer, multiple sclerosis, or other disorders.

and his or her basic physical and mental health, some users may feel relaxed and drowsy, but others feel panicky and upset. Common reactions to marijuana use include:

  • Changed visual perceptions combined with the inability to judge distances accurately. This is one reason why marijuana users are at increased risk of car crashes.
  • Loss of an accurate sense of time.
  • Increased appetite for food.
  • Impaired coordination. The National Highway Traffic Safety Administration (NHTSA) has found that marijuana has a significant effect on people's ability to drive safely for at least three hours after use. Users of marijuana are second only to alcoholics in terms of their involvement in fatal car crashes.
  • Feelings of well-being, power, or importance.
  • Speeded-up heartbeat.
  • Dry mouth and throat.
  • Dilation of the blood vessels in the eyes, giving them a reddened appearance.

About 60 percent of marijuana users have unpleasant sensations while using marijuana. Some people have strongly negative reactions to the drug, including:

  • Feelings of fear, suspicion, or panic
  • Feelings that the environment is unreal or that one's self is unreal
  • Visual hallucinations or hearing voices
  • Rapid changes in mood
  • Unusual tiredness and loss of energy
  • Psychotic episodes (complete loss of contact with reality)

Marijuana has a potential for addiction by itself as well as when it is used in combination with such other drugs as alcohol and cocaine. Of the estimated 6.9 million Americans who were diagnosed in 2003 as being dependent on or abusing illicit drugs, 4.2 million were dependent on or abused marijuana. Addiction to marijuana can have serious long-term consequences for a young person's success in school and the workplace.


Diagnosis of marijuana use is usually determined by a urine test for THC. In most cases, the chemical is detectable for one to five days after the person's last use of marijuana. THC does, however, remain in the fatty tissues of the body for weeks, so that some people fail drug screens for marijuana use as long as twenty-one days after their last use.

There are also blood tests that can be used to screen for marijuana use. They can also be used to distinguish between recent use of the drug and long-term excretion of THC that has been stored in the body.

A more recent diagnostic technique involves analyzing a sample of the person's saliva. This test is particularly useful in evaluating people arrested for driving under the influence of marijuana.


About 100,000 people in the United States seek treatment each year for marijuana addiction. Treatment requires abstaining from use of alcohol, cocaine, and other drugs of abuse as well as marijuana itself. Quitting is difficult because of the side effects that many users experience when they stop using marijuana, including irritability, increased aggressiveness, anxiety, and difficulty sleeping.

They may also find it hard to stay away from peers who are continuing to use the drug or from social activities associated with using marijuana. Successful treatment usually requires a combination of medications to help the person cope with the physical effects of quitting, psychotherapy to help them deal with the emotional issues that attracted them to marijuana, and lifestyle changes to help them avoid relapsing.


The prognosis for people who continue to use marijuana over long periods of time is problematic. A number of long-term risks to educational achievement, physical health, and mental health have been identified:

  • Learning problems, memory problems, and falling behind in school
  • Loss of problem-solving abilities and other life skills
  • Increased risk of lung infections from marijuana contaminated by fungi, and eventual lung cancer, emphysema, or other lung diseases
  • Infertility
  • Increased risk of psychosis
  • Seizures
  • Damage to the heart and cardiovascular system resulting from chronic increased heart rate and rapid changes in blood pressure
  • Increased risk of accidents in the workplace or while driving caused by impaired hand-eye coordination

It is difficult to evaluate the likelihood of a person's long-term successful recovery from addiction to marijuana because many users combine

it with other drugs such as cocaine, alcohol, and amphetamines. Multiple drug use makes it difficult for researchers to determine which treatment methods have the greatest likelihood of success.


Educating young people about the dangers of using marijuana appears to have a limited effect in discouraging use of the drug. The best method of prevention is a healthy family life. Parents who set good examples of responsible use of alcohol and prescription drugs, and who take the time to create strong and loving relationships with their children, can lower the risk that their children will find marijuana and other mood-altering drugs attractive.

The Future

At present there are no medications that specifically target marijuana addiction. Research into the effects of THC on the brain, however, is ongoing and may lead to the development of a medication that would either block the effects of marijuana on the brain or lower its appeal to people.

SEE ALSO AIDS; Alcoholism; Emphysema; Glaucoma; Smoking


Addiction: A chronic disease characterized by compulsive drug use and by long-lasting chemical changes in the brain.

Blunt: A cigar that has been cut open and refilled with marijuana.

Bong: A water pipe used to smoke marijuana.

Dronabinol: A medication that contains synthetic THC, given to relieve nausea and improve appetite in AIDS and cancer patients.

Hashish: A concentrated resin prepared from the flowering tops of hemp plants.

Hit: A single intake of marijuana smoke from a joint or bong.

Joint: A cigarette made with marijuana instead of tobacco.

Reefer: Another name for a marijuana cigarette.

THC: The abbreviation for delta-9-tetrahydrocannabinol, the main mind-altering chemical in marijuana.

For more information


Connolly, Sean. Marijuana. North Mankato, MN: Smart Apple Media, 2007.

Ingram, W. Scott. Marijuana. New York: Chelsea House, 2008. Sanna, E. J. Marijuana: Mind-Altering Weed. Philadelphia: Mason CrestPublishers, 2008.


“Marijuana May Increase Psychosis Risk, Study Says, Refueling Debate on Pot's Dangers.” International Herald Tribune, July 26, 2007. Available online at (accessed May 10, 2008).


Bonsor, Kevin. How Marijuana Works. Available online at (accessed May 10, 2008). This Web site includes a diagram of the specific parts of the brain affected by marijuana.

National Institute on Drug Abuse (NIDA). Research Report: Marijuana Abuse. Available online in PDF format at (updated 2005; accessed May 10, 2008).

NIDA for Teens. Marijuana. Available online at (updated 2002; accessed May 10, 2008).

PBS Online: Close to Home Animations. Marijuana. Available online at (accessed May 10, 2008). Brief animation shows how the active chemicals in marijuana travel to the brain, depending on whether the drug is eaten or smoked.

TeensHealth. Marijuana. Available online at (updated August 2006; accessed May 10, 2008).

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