Marijuana is a green, brown, or gray mix of dried, crumbled parts from the marijuana plant. It can be rolled up and smoked like a cigarette or cigar or smoked in a pipe. Sometimes people mix it in food or inhale it using a vaporizer.
Marijuana can cause problems with memory, learning, and behavior. Smoking it can cause some of the same coughing and breathing problems as smoking cigarettes. Some people get addicted to marijuana after using it for a while. It is more likely to happen if they use marijuana every day, or started using it when they were teenagers.
Some states have approved "medical marijuana" to ease symptoms of various health problems. The U.S. Food and Drug Administration (FDA) has not approved the marijuana plant as a medicine. However, there have been scientific studies of cannabinoids, the chemicals in marijuana. This has led to two FDA-approved medicines. They contain THC, the active ingredient in marijuana. They treat nausea caused by chemotherapy and increase appetite in patients who have severe weight loss from HIV/AIDS. Scientists are doing more research with marijuana and its ingredients to treat many diseases and conditions.
NIH: National Institute on Drug Abuse