Marijuana, which can also be called weed, pot, dope, or cannabis, is the dried flowers and leaves of the cannabis plant. It contains mind-altering (e.g., psychoactive) compounds like tetrahydrocannabinol, or THC, as well as other active compounds like cannabidiol, or CBD, that are not mind-altering.

Although the federal government still prohibits the use, cultivation or sale of cannabis, what is legal actually depends on where you live. As of early 2016, cannabis is legal to some degree in nearly half of U.S. states. However, each state has different restrictions on how cannabis can be used, and even in legal states, it is federally illegal, though the federal government has deferred to the states rights within their borders.
For example, Colorado, Washington and Oregon have legalized cannabis for medical and recreational use.
Other states that have legalized cannabis allow medical use only with a doctors recommendation or prescription, and the patient must register for the states medical program.
And some states and cities have decriminalized cannabis, which means that people who use cannabis pay a fine instead of go to prison. But in those states its still illegal to grow or sell, with prison sentences possible.
Finally, cannabis remains illegal in many states, and users, growers and suppliers can be sent to prison.
Cannabis is illegal in most countries outside of the U.S., although a few have decriminalized use or are in the process of legalizing or decriminalizing cannabis.

There are many differences among the three varieties in terms of their appearance and effect on the body. Pure sativa plants grow tall and look like a Christmas tree. Their leaves are long and narrow, and are light to medium green. Their buds are long and thin and tend to emit a sweet, fruity odor. On the other hand, pure indica plants grow smaller and have a bushy shape. Leaves are short and wide, and theyre dark green and purple. Buds are wider and denser than sativas and tend to emit a strong musky odor.
Sativa plants produce more THC, the psychoactive ingredient that gets people high, whereas indicas produce more CBD, which causes people to relax. Hybrids are a genetic mix of sativa and indica plant characteristics, and their effect on the body is more nuanced than pure varieties. In reality, however, all plants grown commercially are hybrids to one degree or another, with either sativa-dominant or indica-dominant characteristics.

There are many ways of using marijuana, and each one affects users differently. Marijuana can be rolled up and smoked like a cigarette (a joint) or a cigar (a blunt). Marijuana can also be smoked in a pipe. Sometimes people mix it in food and eat it or brew it as a tea (edibles). Smoking oils, concentrates, and extracts from the marijuana plant are on the rise. People who use this practice call it “dabbing.”

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 (e.g., genes), gender, how the drug is taken, and how strong it is.

The marijuana plant has chemicals that may help symptoms for some health problems. More and more states are making it legal to use the plant as medicine for certain conditions. But there isn’t enough research to show that the whole plant works to treat or cure these conditions. Also, the U.S. Food and Drug Administration (FDA)Externalhas not recognized or approved the marijuana plant as medicine.

Because marijuana is often smoked, it can damage your lungs and cardiovascular system (e.g., heart and blood vessels). These and other damaging effects on the brain and body could make marijuana more harmful than helpful as a medicine. Another problem with marijuana as a medicine is that the ingredients aren’t exactly the same from plant to plant. There’s no way to know what kind and how much of a chemical you’re getting.

Two medicines have been made as pills from a chemical that’s like THC, one of the chemicals found in the marijuana plant that makes people feel “high.” These two medicines can treat nausea if you have cancer and make you hungry if you have AIDS and don’t feel like eating. But the chemical used to make these medicines affects the brain also, so it can do things to your body other than just working as medicine.

Another marijuana chemical that scientists are studying, called cannabidiol (CBD), doesn’t make you high because it acts on different parts of the nervous system than THC Scientists think this chemical might help children who have a lot of seizures (when your body starts twitching and jerking uncontrollably) that can’t be controlled with other medicines. Some studies have started to see whether it can help.

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.External

Because marijuana is often smoked, it can damage your lungs and cardiovascular system (e.g., heart and blood vessels). These and other damaging effects on the brain and body could make marijuana more harmful than helpful as a medicine. Another problem with marijuana as a medicine is that the ingredients aren’t exactly the same from plant to plant. There’s no way to know what kind and how much of a chemical you’re getting.

Two medicines have been made as pills from a chemical that’s like THC, one of the chemicals found in the marijuana plant that makes people feel “high.” These two medicines can treat nausea if you have cancer and make you hungry if you have AIDS and don’t feel like eating. But the chemical used to make these medicines affects the brain also, so it can do things to your body other than just working as medicine.

Another marijuana chemical that scientists are studying, called cannabidiol (CBD), doesn’t make you high because it acts on different parts of the nervous system than THC Scientists think this chemical might help children who have a lot of seizures (when your body starts twitching and jerking uncontrollably) that can’t be controlled with other medicines. Some studies have started to see whether it can help.

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