Marijuana is a green or gray mixture of dried, shredded flowers and leaves of the hemp plant (Cannabis sativa). It is the most often used illegal drug in this country. All forms of cannabis are mind-altering (psychoactive) drugs; they all contain THC (delta-9-tetrahydrocannabinol), the main active chemical in marijuana. There are about 400 chemicals in a cannabis plant, but THC is the one that affects the brain the most.

There are many different names for marijuana. Slang terms for drugs change quickly, and they vary from one part of the country to another. They may even differ across sections of a large city.

Terms from years ago, such as pot, herb, grass, weed, Mary Jane, and reefer, are still used. You might also hear the names skunk, boom, gangster, kif, or ganja.

There are also street names for different strains or "brands" of marijuana, such as "Texas tea," "Maui wowie," and "Chronic." A recent book of American slang lists more than 200 terms for various kinds of marijuana.

Marijuana's effect on the user depends on the strength or potency of the THC it contains. THC potency has increased since the 1970s but has been about the same since the mid-1980s. The strength of the drug is measured by the average amount of THC in test samples confiscated by law enforcement agencies.

Long-term studies of high school students and their patterns of drug use show that very few young people use other drugs without first trying marijuana. The risk of using cocaine has been estimated to be more than 104 times greater for those who have tried marijuana than for those who have never tried it. Although there are no definitive studies on the factors associated with the movement from marijuana use to use of other drugs, growing evidence shows that a combination of biological, social, and psychological factors are involved.

Marijuana affects the brain in some of the same ways that other drugs do. Researchers are examining the possibility that long-term marijuana use may create changes in the brain that make a person more at risk of becoming addicted to other drugs, such as alcohol or cocaine. While not all young people who use marijuana go on to use other drugs, further research is needed to determine who will be at greatest risk.

Some users, especially someone new to the drug or in a strange setting, may suffer acute anxiety and have paranoid thoughts. This is more likely to happen with high doses of THC. These scary feelings will fade as the drug's effects wear off. When the early effects fade, over a few hours, the user can become very sleepy. In rare cases, a user who has taken a very high dose of the drug can have severe psychotic symptoms and need emergency medical treatment. Other kinds of bad reactions can occur when marijuana is mixed with other drugs, such as PCP or cocaine.

Those who become more heavily involved with marijuana can become dependent, and that is their prime reason for using the drug. Others mention psychological coping as a reason for their use - to deal with anxiety, anger, depression, boredom, and so forth. But marijuana use is not an effective method for coping with life's problems, and staying high can be a way of simply not dealing with ones problems.

There are some signs you might be able to see.
If someone is high on marijuana, he or she might :