MARIJUANA, COCAINE, METHAMPHETAMINE, and heroin are the four most common illegal drugs to which teens become addicted. All have serious health risks and are associated with high rates of violence, medical and psychiatric problems, arrest and imprisonment, and overdose.

Marijuana

Marijuana (weed, bud, pot, herb, and reefer) consists of the dried hemp plant Cannabis sativa. The active ingredient in marijuana is called THC, with mild mood-altering and disorienting effects. The most common way teens use marijuana is by smoking a small hand-rolled cigarette, called a joint, but the drug is also smoked in the form of cigars hollowed out and packed with marijuana, in pipes, and can be mixed into food and eaten.

According to the National Institute on Drug Abuse, the effects of marijuana are mostly pleasurable:

It's common for marijuana users to become engrossed with ordinary...