Cannabis (marijuana, hashish, and hash oil) is also known as weed, pot, reefer, joint, Mary Jane, ganja, grass, sinsemilla, and dope. Additionally, blunts are cigars emptied of some tobacco and refilled with marijuana. Marijuana has been described as the most commonly used illegal drug in the United States. In 2013, there were 19.8 million current users aged 12 and older, up from 14.5 million users in 2007.30 Marijuana laws are changing and may result in an increase in use. As of January 2017, eight states (Alaska, California, Colorado, Maine, Massachusetts, Nevada, Oregon and Washington) and the District of Columbia allow the recreational use of marijuana.3,36 An additional 21 states allow for the use of medical marijuana. To view a map of marijuana legalization status, visit

Marijuana increases dopamine, which creates the euphoria or “high” associated with its use. A user may feel the urge to smoke marijuana again and again to re-create that experience. Repeated use could lead to addiction – a disease where people continue to do something, even when they are aware of the severe negative consequences at the personal, social, academic, and professional levels.

Cannabis may be smoked as a cigarette or in a pipe, as well as added to foods. A favorite way to use marijuana is through a “bong” in which the smoke is drawn through a layer of water that cools the smoke and removes some of the tar and irritants.

When marijuana is smoked, tetrahydrocannabinol (THC) rapidly passes from the lungs into the bloodstream, which carries the chemical to the brain and other organs throughout the body.

Contrary to common belief, marijuana is addictive. Estimates from research suggest that about 9% of users become addicted to marijuana; this number increases to 17% among those who start young. People who use marijuana may also experience a withdrawal syndrome when they stop using the drug. This withdrawal is similar to what happens to tobacco smokers when they quit – people report being irritable, having sleep problems, and loosing weight, which can last for several days to a few weeks after drug use is stopped. Relapse is common during this period, as users also crave the drug to relieve these symptoms.28