Globally, marijuana is the most commonly used illicit drug. Classified as a Schedule 1 controlled substance, marijuana is a mood-altering drug that affects almost every organ in the body.
In 2017, 6 percent or about 1 in 16 high school seniors in the United States reported using marijuana (cannabis) every day. The number of 12th graders who think marijuana use is risky has halved in the last 20 years.

According to the 2013 National Survey on Drug Use and Health (NSDUH), 19.8 million, or 80.6 percent of people who used illicit drugs in the U.S. used marijuana in the month before being surveyed.

People can smoke marijuana, inhale it through vapor, brew it as a tea, apply it as a balm, or eat it in products, such as brownies or chocolate bars.

Some people use medical marijuana to treat chronic pain, muscle spasticity, anorexia, nausea, and sleep disturbances.

Medical marijuana refers to either whole marijuana or its ingredients, such as cannabidiol (CBD), which forms the base of a limited number of approved medications.

Medical marijuana is not subject to governmental standardization, making its ingredients and potency unknown. It is not legal in all states.

Fast facts on marijuana:
The primary psychoactive ingredient in marijuana is delta-9-tetrahydro-cannabidinol (THC).
Marijuana contains more than 120 compounds, which are likely to have different properties.
The effects of recreational marijuana use include lightheadedness, a feeling of relaxation, increased appetite, and reduced blood pressure.