After alcohol, marijuana is the most widely used and abused substance in United States. The active ingredient in marijuana is tetrahydrocannabinol or THC which produces feelings of happiness, euphoria, and decreased anxiety upon consumption. Unlike popular belief, marijuana can be addictive and highly damaging to health. It stimulates the production of dopamine and with long term use; the brain fails to produce required amounts of dopamine without the drug, which results into excessive carvings and the appearance of withdrawal symptoms. Because of its harmful effects, a large number of addicts (about 15%) willingly choose a rehab program. Marijuana also serves as a gateway drug and can lead to the usage of even more harmful drugs such as cocaine or meth. A number of street names are given to marijuana such as weed, pot, Mary Jane, hash, ganja, herb and bud.