What We Know About Marijuana

Marijuana, which can also be called cannabis, weed, pot, or dope, refers to the dried flowers, leaves, stems, and seeds of the cannabis plant. The cannabis plant contains more than 100 compounds (or cannabinoids). These compounds include tetrahydrocannabinol (THC), which is impairing or mind-altering, as well as other active compounds, such as cannabidiol (CBD). CBD is not impairing, meaning it does not cause a “high”.1

Marijuana can be used in a number of ways.2,3 The most common ways include:

  • Smoked in joints (like a cigarette), in blunts (cigars or cigar wrappers that have been partly or completely refilled with marijuana), or in bongs (pipes or water pipes)
  • Vaped using electronic vaporizing devices (like vape pens) or other vaporizers
  • Mixed or infused into foods or drinks (called edibles) like cookies, cakes, or brownies, or tea, cola, or alcohol

Additionally, some people inhale the oil concentrates and other extracts from the cannabis plant—this is known as dabbing. THC oils and concentrates used in vaping and dabbing often involve using highly concentrated forms of THC and may contain additives or be contaminated with other substances that may be harmful.4

How marijuana affects a person depends on several factors, including:

  • Amount of marijuana taken
  • Frequency of marijuana use
  • Use of marijuana with other substances (e.g., alcohol or other drugs), which could increase risk of harm5
  • Mode of marijuana use (e.g., consuming edibles or products with high THC concentration can have delayed or unpredictable effects and increases the risk of overdose or poisoning5)
  • Previous experience with marijuana or other drugs
  • Biology (e.g., genes, DNA)
  • Sex (e.g., women may experience more dizziness after using marijuana compared to men6)
Marijuana as Medicine

The Food and Drug Administrationexternal icon (FDA) has approved one plant-based marijuana drug called Epidiolex, which contains a purified form of CBD. The prescription medication is approved for treating seizures associated with two rare and severe forms of epilepsy (Lennox-Gastaut syndrome and Dravet syndrome) as well as seizures associated with a rare genetic disorder called tuberous sclerosis complex. The FDA has also approved two medicines (dronabinol [brand names: Marinol and Syndros] and nabilone [brand name: Cesamet]) that are made from a synthetic or lab-made chemical that mimics THC. These medicines are used to treat nausea in patients with cancer who are having chemotherapy treatment, and to increase appetite in individuals with AIDS who do not feel like eating (wasting syndrome). These approved products are only available with a prescription from a licensed healthcare provider. There are currently no other FDA-approved uses for cannabis or its derivatives.

Health Effects and Risks

There are health risks associated with using marijuana regardless of how it is used. These include:

Marijuana Use Disorder

Approximately 3 in 10 people who use marijuana have marijuana use disorder.7 Some signs and symptoms of marijuana use disorder include trying but failing to quit using marijuana or giving up important activities with friends and family in favor of using marijuana.8 The risk of developing marijuana use disorder is stronger in people who start using marijuana during youth or adolescence and who use marijuana more frequently.9

Brain Health

Marijuana use directly affects brain function—specifically the parts of the brain responsible for memory, learning, attention, decision making, coordination, emotions, and reaction time.5,10 Developing brains, such as those in babies, children, and teenagers, are especially susceptible to the harmful effects of marijuana and THC.5,10

Heart Health

Marijuana can make the heart beat faster and can make blood pressure higher immediately after use.11,12 It could also lead to increased risk of stroke, heart disease, and other vascular diseases.13-17


Marijuana, like alcohol, negatively affects several skills required for safe driving. It can slow reaction time and ability to make decisions.5,18

  • Marijuana can impair coordination and distort perception.5,18
  • The use of multiple substances (such as marijuana and alcohol) at the same time can increase impairment.19
  • Some studies have shown an association between marijuana use and car crashes; however, more research is needed.5,19

Lung Health

Smoked marijuana, regardless of how it is smoked, can harm lung tissues and cause scarring and damage to small blood vessels.20,21 While more research on the health consequences of breathing secondhand marijuana smoke is needed, there is concern that it could cause harmful health effects, including among children.

Mental Health

Marijuana use has been linked to social anxiety, depression, and schizophrenia (a type of mental illness where people might see or hear things that aren’t really there), but scientists don’t yet fully understand the relationships between these mental health disorders and marijuana use.6,22

Unintentional Poisoning

Edibles, or food and drink products infused with marijuana, have some different risks than smoked marijuana, including a greater risk of poisoning. Children can mistake edibles for regular food or candy. Consuming marijuana can make children very sick. Since marijuana use has been legalized in some states, unintentional poisonings in children have increased, with some instances requiring emergency medical care.23

If you use marijuana products, keep them in childproof containers and out of the reach of children. For additional questions, you can contact your healthcare provider, your health department, your local or regional poison control center at 1-800-222-1222, or 911 if it’s an emergency.

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