Frequently Asked Questions

Marijuana is a mind-altering (e.g. psychoactive) drug that comes from the cannabis plant. Even though a lot of people use the word “marijuana” when talking about cannabis in general, marijuana is actually just the dried flowers and leaves of the plant. Other common names for marijuana are weed, pot, dope, or green. Sometimes, the term “marijuana” is used to describe edible products, like foods or beverages that contain the active parts of marijuana.

Marijuana can be consumed by smoking or inhaling it, eating it in various kinds of products (i.e., edibles), and absorbing it by applying products on the skin or in the mouth.

Most people who use marijuana smoke it in a joint, which is like a cigarette, or in a bong, which is a water pipe. To avoid inhaling smoke, more people are vaping—using vaporizers that allow the person to inhale vapor and not smoke. Another popular method on the rise is smoking or vaping THC-rich resins taken from the marijuana plant, a practice called dabbing.

There are many different types of marijuana, and the strength of the drug can vary widely depending on the type and how it is consumed.

The two best-known compounds in marijuana are tetrahydrocannabinol, or THC, and cannabidiol, or CBD. THC has psychoactive (mind-altering) effects, including altered senses and mood changes, and can lead to changes in behavior.

THC has psychoactive effects, including altered senses and mood changes, and can lead to changes in behavior. THC rapidly reaches every organ in the body, including the brain, and attaches to specific receptors on nerve cells. Activation of these receptors in the brain affects pleasure, memory, thinking, concentration, movement, coordination, appetite, pain, and sensory and time perception. Some of these effects last only as long as marijuana is in the body, while others may build up over time to cause longer-lasting problems. ^{[46, 47]} CBD, however, does not produce euphoria or intoxication.

Both THC and CBD are being studied for their potential as treatments for several serious health conditions.

Marijuana is illegal under federal law and on all federally owned land, including national parks. However, some states, cities, and tribes have passed legislation that allow the use of marijuana for medical or recreational reasons. Learn more about marijuana laws.

Like any other drug, marijuana’s effects on a person depends on a number of factors, including the person’s previous experience with the drug or other drugs, biology (i.e., genes), gender, how the drug is taken, and how strong it is.

The term medical marijuana refers to using the whole, unprocessed marijuana plant to treat a disease or symptom. The US Food and Drug Administration (FDA) has not recognized or approved the marijuana plant as medicine. However, scientific study of the chemicals in marijuana, called cannabinoids, has led to three FDA-approved medications that contain cannabinoid chemicals in pill or liquid form, and scientists continue to study safe ways patients can use THC and other marijuana ingredients as medicine.

Yes, about 1 in 10 marijuana users will become addicted. For people who begin using younger than 18, that number rises to 1 in 6.^[1-3] For more information visit CDC’s section on addiction or the National Institute on Drug Abuse’s pages on addiction science.

Some of the signs that someone might be addicted to marijuana include:

• Trying but failing to quit using marijuana.
• Giving up important activities with friends and family in favor of using marijuana.
• Using marijuana even when it is known that it causes problems at home, school, or work.^[4]

People who are addicted to marijuana are at a higher risk of the negative consequences of using the drug, such as problems with attention, memory, and learning. For more information visit CDC’s section on addiction or the National Institute on Drug Abuse’s pages on addiction science.

For more on the health risks and effects of marijuana visit CDC’s web page on marijuana and health effects.

A fatal overdose is unlikely, but that doesn’t mean marijuana is harmless. In fact, the potency—determined by the amount of THC in the marijuana—of current strains may lead to poisonings, particularly when eaten or swallowed. Also, people can and do injure themselves because of marijuana’s effects on judgment, perception, movement, and coordination. For more information visit CDC’s section on poisoning. If you think you or someone you love has had too much marijuana and is having serious problems, call 911.

When people mix marijuana and alcohol together at one time, the results can be unpredictable. For example, when people smoke marijuana and drink alcohol at the same time they can have nausea or vomiting, or they can react with panic, anxiety or paranoia. Mixing cannabis with alcohol can also increase the risk of psychotic symptoms such as seeing or hearing things that aren’t really there (hallucinations) for vulnerable people.^[54] Alcohol and marijuana use combined also appears to increase the risk of motor vehicle crashes more than either substance used on its own.^{[55, 56]}

Synthetic cannabinoids (e.g. synthetic marijuana, K2, Spice, Spike)—or plants sprayed with unknown chemicals—are dangerous and unpredictable. Synthetic cannabinoids are not marijuana, but like THC, they bind to the same cannabinoid receptors in the brain and other organs.

Research shows that synthetic cannabinoids affect the brain much more powerfully than marijuana creating unpredictable and, in some cases, life-threatening effects including nausea, anxiety, paranoia, brain swelling, seizures, hallucinations, aggression, heart palpitations, and chest pains. For additional questions around synthetic cannabinoids, visit CDC’s National Center for Environmental Health page on synthetic marijuana or the National Institute on Drug Abuse page on synthetic marijuana.

If someone you know has used synthetic cannabinoids and needs help, you can take the following steps:

• Call 911 immediately if someone stops breathing, collapses, or has a seizure. These symptoms can be life threatening and require immediate medical attention.
• Call your local poison center at 1-800-222-1222.
• Call your doctor.

Using marijuana and tobacco at the same time may lead to more severe health effects than using either one alone, including:

• Increased exposure to harmful chemicals, causing greater risks to the lungs, respiratory organs as well as the cardiovascular system.
• Increased addiction to either substance.
• Having a harder time quitting either substance.^{[2, 57-60]}

More research is needed to understand if marijuana is a “gateway drug”  -  a drug that is thought to lead to the use of more dangerous drugs (such as cocaine or heroin). For more on why, visit risk of using other drugs.

Marijuana use during pregnancy can be harmful to a baby’s health. For more information visit What You Need to Know about Marijuana Use and Pregnancy [PDF 229KB].

Chemicals from marijuana can be passed to your baby through breast milk. THC is stored in fat and is slowly released over time, meaning an infant could be exposed for a longer period of time. However, data on the effects of marijuana exposure to the infant through breastfeeding are limited and conflicting. To limit potential risk to the infant, breastfeeding mothers should reduce or avoid marijuana use.^[64-66] For more information visit What You Need to Know About Marijuana Use and Pregnancy [PDF 229KB].

Yes, secondhand marijuana smoke contains tetrahydrocannabinol (THC), the chemical responsible for most of marijuana’s psychological effects, and many of the same toxic chemicals in smoked tobacco.^{[28, 34, 35]}

Yes, there is growing scientific evidence that heavy, regular use of marijuana that begins during the teen years may lower a person’s IQ and interfere with other aspects of school, social life and well-being.^{[6, 67-70]} Teen marijuana users are also more likely to become addicted to marijuana than people who start using the drug when they are older.^[2] Researchers have also found that some marijuana users have an increased risk for psychosis, a serious mental disorder where people have false thoughts (delusions) or see or hear things that aren’t there (hallucinations).^[64] For more information visit What You Need to Know About Marijuana Use in Teens [PDF 224KB].

You may know that smoking marijuana can pose risks for a person’s physical health and brain development, especially for teens. But here are some other things you should know:

• Teens who drink alcohol and smoke tobacco are more likely to try marijuana. Teens are also more likely to use marijuana if their parents or friends use it, and less likely to use marijuana if their parents do not approve of it.^[71]
• Teens may use marijuana because they believe it is not as harmful as tobacco^[72], but they should know using marijuana can have lasting impact on the teen brain. Research suggests that the effects on attention, memory, and learning can be long-term and even permanent in people who begin using marijuana regularly as teens. Lost mental abilities might not fully return even if a person quits using marijuana as an adult.
• In addition to psychosis, regular teen marijuana use has been linked with increased risk for several mental problems, including depression, anxiety, suicidal thoughts, and personality disturbances.
• New formulations of marijuana or marijuana products (e.g., edibles, including candies and sodas, as well as concentrated marijuana oils used in vaporizer pens) have become a popular alternative to smoking marijuana.

For more information visit What You Need to Know about Marijuana Use in Teens [PDF 224] or the National Institutes of Drug Abuse’s Facts Parents Need to Know.

Eating or drinking foods that contain marijuana (i.e., edibles) has some different risks than smoking marijuana. Edibles take longer to digest and produce a high. Therefore, people may consume more to feel the effects faster, leading to dangerous results. For more information on marijuana poisoning visit CDC’s web page on marijuana and health effects.

There is not enough evidence yet to know the specific health effects of using marijuana with vaporizers, or using concentrated waxes or oils made from different parts of the marijuana plant. However, we do know:

• These products can have a lot more THC than other forms of marijuana and the extraction process is not regulated, which means that strength and purity can vary from product to product.
• Some of these products are very high in THC (up to 80%), which increases the likelihood of poisoning.
• Using vaporizers for marijuana may also expose the user to toxic substances, depending on construction material and heating temperatures of the devices.^[3]

Smoked marijuana has many of the same cancer-causing substances as smoked tobacco, but there are still a lot of unanswered questions around the potential for causing chronic diseases such as heart attacks, cancer, and lung diseases. Here’s what we do know:

• Heart attack and strokes: The compounds in marijuana can affect the circulatory system in the heart and brain and may increase the risk of heart attacks and ischemic strokes.^[22]
• Cancer: It is not yet known if marijuana can cause cancer, partly because most people who use marijuana also use tobacco, a substance that does cause cancer.^[13] More research is needed to understand the full impact of marijuana use on cancer.
• Lung health: Smoke from marijuana contains many of the same toxins, irritants and carcinogens Smoke from marijuana contains toxins, irritants, and carcinogens.^{[24, 25]} This can result in a greater risk of bronchitis, cough, and phlegm production.

For more information on marijuana and chronic disease see CDC’s web page on marijuana and health effects.