Marijuana is the most commonly used illicit drug in the United States. It is a dried, shredded mixture of the hemp plant Cannabis sativa. It is typically smoked  rolled up as a cigarette,  in a pipe, or  in a bong (a water pipe). It can also be smoked in blunts, which are cigars where the tobacco is gutted and filled with marijuana. The main active chemical in marijuana is THC (delta-9-tetrahydrocannabinol). Certain nerve cells in the brain have protein receptors that bind to THC. Once this binding occurs, THC creates a series of cellular reactions that lead to the high associated with marijuana.
Some users become dependent on the drug, and the prevalence of such dependence may be especially pronounced among adolescents and young adults. A study that involved adolescents between the ages of 12 and 18 years found that approximately 4.3% met the DSM-IV criteria for dependence on marijuana, which was a larger percentage than those who met criteria for alcohol dependence (3.5%). In addition, according to the 1991 and 1993 NHSDA surveys, 14.4% of the adolescent users aged 12-17 years were dependent on marijuana.(2) In contrast, according to the National Comorbidity Survey (NCS) conducted from 1990 to 1992 including people of 15 to 54 years of age, almost half of the sample (46.3%) reported using marijuana, but only 4.2% met the criteria for lifetime dependence.
The short term health effects of marijuana include (1):
The frequent use of marijuana may result in :
Street names for marijuana include bud, grass, herb, homegrown, Jane, pot, and weed.