Cannabis is the most widely used illicit drug worldwide. Roughly 4% of adults aged 15 and up smoke marijuana in a given year. More than 25 million Americans have smoked marijuana in the last month. Yet despite its prevalence, cannabis use remains a mystery to many people, with misconceptions running rampant about what it does to our bodies and our minds. In truth, research has shown that cannabis has helped people live better lives by easing pain, suppressing seizures, relieving PTSD symptoms, and more.
What Is Marijuana?
Marijuana is a green, brown, or gray mixture of dried, shredded flowers and leaves of the hemp plant Cannabis sativa. The main active chemical in marijuana is THC (tetrahydrocannabinol). Another common term for marijuana is pot.
How Do People Use Cannabis?
People can use marijuana by smoking it in hand-rolled cigarettes (joints), pipes or water pipes (bongs), or they can smoke it in blunts—which are cigars that have been emptied of tobacco and refilled with marijuana. People also brew their own beer and wine with marijuana or add it to food and eat it. People who smoke marijuana can also use other devices to inhale and ingest it. For example, a vaporizer heats cannabis to a temperature that is too low to cause much psychoactive effect. A special balloon called a vape pen is heated by an electric current and used to heat the cannabis material so that it can be inhaled into the lungs.
How Does Marijuana Affect People’s Brains?
THC, one of the active chemicals in marijuana, acts on specific areas of the brain that influence mood and perception. THC can affect memory and learning, coordination and balance, and sensitivity to pain.
How Is Marijuana Used?
The frequency of marijuana use in the United States has increased sharply in recent years. An estimated 6% of Americans aged 12 or older say they have used marijuana at some point in the past year, up from 4.5% in 2005–2006; similar data are not available for younger ages. Marijuana is used mostly by young people—about 8.9% of those aged 12–17 have reported using it at least once during the 12 months preceding the survey (down from 10.1% in 2005–2006). Among adults aged 18 or older, 1.5% say they have used it in the past month, up from 1.4% in 2005–2006.
Cannabis use is linked to mental illness and certain physical health conditions. Long-term cannabis users are more likely than nonusers to develop chronic bronchitis (a lung disease that causes coughing, wheezing, and shortness of breath), as well as a variety of respiratory problems, such as obstructed airways infrequently leading to cancer. Cannabis smoke contains many of the same toxins, irritants, and carcinogens as tobacco smoke. The active ingredients in marijuana, THC and other substances that cause the “high,” can be absorbed by the lungs.
Chronic marijuana use can also lead to impaired driving and an increased risk of emergency-department visits for car crashes. Scientific studies have linked marijuana use to decreased motivation, attention, and decision-making ability. In addition, heavy marijuana users are at greater risk for problems with memory and thinking.
Chronic marijuana users may experience occasional “munchies”—a strong desire to eat high calorie foods (such as cookies or ice cream) after using cannabis. Marijuana is a transient substance; it gets stored in fat cells where it stays for days or weeks before being released into the blood stream again. This process contributes to the chronic effects cannabis has on eating behavior and may make people who use marijuana excessively eat more than they should.
Marijuana is also linked to serious mental health problems, like schizophrenia, and mood disorders. Young people who use marijuana have a significantly higher chance of developing schizophrenia or other psychosis later in life compared to those who never use the drug. And, animals exposed to THC before birth or in early life can exhibit problems similar to those shown by humans. More research needs to be done to confirm this link, but many scientists are convinced that it exists. Research also shows that using marijuana puts users at risk for developing depression and anxiety.
How Does Marijuana Affect Driving?
Marijuana smoke contains many of the same toxins and irritants as tobacco smoke. The active ingredients in marijuana, THC and other substances that cause the “high,” are absorbed by the lungs. When people smoke marijuana, they may have more difficulty controlling speed and steering their vehicle. Also, people who smoke marijuana often also smoke tobacco cigarettes. In addition, smoking pot lowers a driver’s sense of time and distance, which can lead to slower reaction times and erratic driving.
How Does Marijuana Affect Teens?
People typically start using marijuana during their early teens, but young teens seem to start earlier today than they did 20 or 30 years ago. Merely experimenting with marijuana can affect a teen’s development and may make them more likely to try other drugs or alcohol.
How Does Marijuana Affect Men?
Marijuana is the substance most commonly used by people seeking treatment for drug addiction. It is also linked to violence, including domestic abuse and sexual assault. For more information about marijuana use, see our Infographic: Marijuana Use Among Adults.
Many teens who use marijuana think it makes them smarter, cooler, or more creative. However, there’s mounting evidence that marijuana use actually does just the opposite—it may lower intelligence and lead to long-term problems with memory and learning. Studies of groups of people who start using marijuana as teens have shown a significant drop in IQ, with some mental abilities being affected more than others. Among young adults who are chronic heavy users of marijuana (smoking pot at least five times a week), studies have found that they did poorly on tests of memory and reaction time. Workers who smoke marijuana regularly over long periods of time may have trouble remembering to do simple things like taking medication or keeping appointments on time. Marijuana’s effects on intelligence and learning can last for weeks or months after the high is gone.
Heavy use can make people less goal-oriented and more easily bored, so they give up more easily when something is hard. Using pot can also make people less likely to try to accomplish tasks that are hard or take a long time. Strong evidence shows that heavy marijuana users are less likely than non-users to finish school, get jobs, and have healthy, stable relationships. Many studies show a strong link between regular marijuana use and poor performance at school or work.