Marijuana refers to the dried leaves, flowers, stems, and seeds from the hemp plant, Cannabis sativa. The plant contains the mind-altering chemical delta-9-tetrahydrocannabinol (THC) and other related compounds. Extracts with high amounts of THC can also be made from the cannabis plant. Marijuana is the most commonly used illicit drug in the United States.1 Its use is widespread among young people. According to a yearly survey of middle and high school students, rates of marijuana use have steadied in the past few years after several years of increase. However, the number of young people who believe marijuana use is risky is decreasing.
People smoke marijuana in hand-rolled cigarettes (joints) or in pipes or water pipes (bongs). They also smoke it in blunts—emptied cigars that have been partly or completely refilled with marijuana. To avoid inhaling smoke, more people are using vaporizers. These devices pull the active ingredients (including THC) from the marijuana and collect their vapor in a storage unit. A person then inhales the vapor, not the smoke. Users can mix marijuana in food (edibles), such as brownies, cookies, or candy, or brew it as a tea. A newly popular method of use is smoking or eating different forms of THC-rich resins
Marijuana smoke irritates the lungs, and frequent marijuana smokers can have the same breathing problems that tobacco smokers have. These problems include daily cough and phlegm, more frequent lung illness, and a higher risk of lung infections. Researchers still do not know whether marijuana smokers have a higher risk for lung cancer.
Marijuana raises heart rate for up to 3 hours after smoking. This effect may increase the chance of heart attack. Older people and those with heart problems may be at higher risk
Marijuana use during pregnancy is linked to increased risk of both brain and behavioral problems in babies. If a pregnant woman uses marijuana, the drug may affect certain developing parts of the fetus’s brain. Resulting challenges for the child may include problems with attention, memory, and problem-solving. Additionally, some research suggests that moderate amounts of THC are excreted into the breast milk of nursing mothers. The effects on a baby’s developing brain are still unknown.
Marijuana use has also been linked to other mental health problems, such as depression, anxiety, and suicidal thoughts among teens. However, study findings have been mixed.
Compared to nonusers, heavy marijuana users more often report the following:
Users also report less academic and career success. For example, marijuana use is linked to a higher likelihood of dropping out of school.
Some research suggests that marijuana use is likely to come before use of other drugs. Marijuana use is also linked to addiction to other substances, including nicotine. In addition, animal studies show that the THC in marijuana makes other drugs more pleasurable to the brain. Although these findings support the idea of marijuana as a “gateway drug,” the majority of people who use marijuana don’t go on to use other “harder” drugs.
Contrary to common belief, marijuana can be addictive. Research suggests that 30 percent of users may develop some degree of problem use, which can lead to dependence and in severe cases takes the form of addiction. People who begin using marijuana before age 18 are 4 to 7 times more like than adults to develop problem use. Dependence becomes addiction when the person can’t stop using marijuana even though it interferes with his or her daily life.
Long-term marijuana users trying to quit report withdrawal symptoms that make quitting difficult. These include:
Behavioral support has been effective in treating marijuana addiction. Examples include therapy and motivational incentives (providing rewards to patients who remain substance free). No medications are currently available to treat marijuana addiction. However, continuing research may lead to new medications that help ease withdrawal symptoms, block the effects of marijuana, and prevent relapse.