What is marijuana?
Marijuana (grass, pot, weed) is the common name for a crude drug made from the plant Cannabis sativa. The main mind-altering (psychoactive) ingredient in marijuana is THC (delta-9-tetrahydrocannabinol), but more than 400 other chemicals also are in the plant. A marijuana "joint" (cigarette) is made from the dried particles of the plant. The amount of THC in the marijuana determines how strong its effects will be. The type of plant, the weather, the soil, the time of harvest, and other factors determine the strength of marijuana. The strength of today's marijuana is as much as ten times greater than the marijuana used in the early 1970s. This more potent marijuana increases physical and mental effects and the possibility of health problems for the user. Hashish, or hash, is made by taking the resin from the leaves and flowers of the marijuana plant and pressing it into cakes or slabs. Hash is usually stronger than crude marijuana and may contain five to ten times as much THC. Pure THC is almost never available, except for research. Substances sold as THC on the street often turn out to be something else, such as PCP.

What are some of the immediate effects of smoking marijuana?
Some immediate physical effects of marijuana include a faster heartbeat and pulse rate, bloodshot eyes, and a dry mouth and throat. No scientific evidence indicates that marijuana improves hearing, eyesight, and skin sensitivity. Studies of marijuana's mental effects show that the drug can impair or reduce short-term memory, alter sense of time, and reduce ability to do things which require concentration, swift reactions, and coordination, such as driving a car or operating machinery.

Are there any other adverse reactions to marijuana?
A common bad reaction to marijuana is the "acute panic anxiety reaction." People describe this reaction as an extreme fear of "losing control," which causes panic. The symptoms usually disappear in a few hours.

What about psychological dependence on marijuana?
Long-term regular users of marijuana may become psychologically dependent. They may have a hard time limiting their use, they may need more of the drug to get the same effect, and they may develop problems with their jobs and personal relationships. The drug can become the most important aspect of their lives.

What are the dangers for young people?
One major concern about marijuana is its possible effects on young people as they grow up. Research shows that the earlier people start using drugs, the more likely they are to go on to experiment with other drugs. In addition, when young people start using marijuana regularly, they often lose interest and are not motivated to do their schoolwork. The effects of marijuana can interfere with learning by impairing thinking, reading comprehension, and verbal and mathematical skills. Research shows that students do not remember what they have learned when they are "high".

How does marijuana affect driving ability?
Driving experiments show that marijuana affects a wide range of skills needed for safe driving -- thinking and reflexes are slowed, making it hard for drivers to respond to sudden, unexpected events. Also, a driver's ability to "track" (stay in lane) through curves, to brake quickly, and to maintain speed and the proper distance between cars is affected. Research shows that these skills are impaired for at least 4-6 hours after smoking a single marijuana cigarette, long after the "high" is gone. If a person drinks alcohol, along with using marijuana, the risk of an accident greatly increases. Marijuana presents a definite danger on the road.

Does marijuana affect the human reproductive system?
Some research studies suggest that the use of marijuana during pregnancy may result in premature babies and in low birth weights. Studies of men and women may have a temporary loss of fertility. These findings suggest that marijuana may be especially harmful during adolescence, a period of rapid physical and sexual development.

How does marijuana affect the heart?
Marijuana use increases the heart rate as much as 50 percent, depending on the amount of THC. It can cause chest pain in people who have a poor blood supply to the heart - and it produces these effects more rapidly than tobacco smoke does.

How does marijuana affect the lungs?
Scientists believe that marijuana can be especially harmful to the lungs because users often inhale the unfiltered smoke deeply and hold it in their lungs as long as possible. Therefore, the smoke is in contact with lung tissues for long periods of time, which irritates the lungs and damages the way they work. Marijuana smoke contains some of the same ingredients in tobacco smoke that can cause emphysema and cancer. In addition, many marijuana users also smoke cigarettes; the combined effects of smoking these two substances creates an increased health risk.

Can marijuana cause cancer?
Marijuana smoke has been found to contain more cancer-causing agents than is found in tobacco smoke. Examination of human lung tissue that had been exposed to marijuana smoke over a long period of time in a laboratory showed cellular changes called metaplasia that are considered precancerous. In laboratory test, the tars from marijuana smoke have produced tumors when applied to animal skin. These studies suggest that it is likely that marijuana may cause cancer if used for a number of years.

How are people usually introduced to marijuana?
Many young people are introduced to marijuana by their peers - usually acquaintances, friends, sisters, and brothers. People often try drugs such as marijuana because they feel pressured by peers to be part of the group. Children must be taught how to say no to peer pressure to try drugs. Parents can get involved by becoming informed about marijuana and by talking to their children about drug use.

What is marijuana "burnout"?
"Burnout" is a term first used by marijuana smokers themselves to describe the effect of prolonged use. Young people who smoke marijuana heavily over long periods of time can become dull, slow moving, and inattentive. These "burned-out" users are sometimes so unaware of their surroundings that they do not respond when friends speak to them, and they do not realize they have a problem.

How long do chemicals from marijuana stay in the body after the drug is smoked?
When marijuana is smoked, THC, its active ingredient, is absorbed by most tissues and organs in the body; however, it is primarily found in fat tissues. The body, in its attempt to rid itself of the foreign chemical, chemically transforms the THC into metabolites. Urine tests can detect THC metabolites for up to a week after people have smoked marijuana. Tests involving radioactively labeled THC have traced these metabolites in animals for up to a month.

Source: National Institute on Drug Abuse, 1984.

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