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Cannabis Frequently Asked Questions

Key points

  • Answers to the most frequently asked questions relating to cannabis based on current research.
  • Answers to the most frequently asked questions relating to CBD based on current research.
Green cannabis leaf

Cannabis FAQs

Cannabis—which can also be called marijuana, weed, pot, or bud—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

Cannabis can be used in a number of ways.23 Cannabis can be smoked in joints (like a cigarette), in blunts (cigars or cigar wrappers that have been partly or completely refilled with cannabis), or in bongs (pipes or water pipes). Cannabis also can be mixed or infused into foods like cookies, cakes, or brownies (called edibles) and can be infused in drinks.

It can be vaped using electronic vaporizing devices (i.e., e-cigarettes or vape pens) or other vaporizers. Compounds (or cannabinoids) in cannabis can also be extracted to make oils and concentrates that can be vaped or inhaled. Smoking oils, concentrates, and extracts from the cannabis plant, known as "dabbing," is on the rise.4 Health and safety risks exist for each of the different ways of using cannabis.

Cannabis products that contain tetrahydrocannabinol (THC) can have health risks no matter how they are used because THC is impairing. THC can affect memory, attention, decision-making, and risk-taking.15

Health and safety risks exist for each of the different ways of using cannabis, and scientists do not have enough evidence to say that using cannabis in one way is safer than another. For example, smoking cannabis can expose you and those around you to harmful chemicals.6

Oils and concentrates used in vaping and dabbing (which is a specific method of inhaling THC concentrates) often have highly concentrated forms of THC and may contain additives or be contaminated with other substances.78 The effects of using these more concentrated forms of THC are not well understood but may include higher risk of developing cannabis use disorder.19 Vaping has also been linked to lung injury.10

Marijuana and E-cigarette, or Vaping Use-Associated with Lung Injury (EVALI)

In 2019, a national outbreak of lung injury associated with vaping occurred.10 Data from patient reports and product testing showed tetrahydrocannabinol (THC)-containing vaping products that also contained vitamin E acetate were linked to most cases. This outbreak resulted in over 2,800 emergency department visits and 68 confirmed deaths. More information about the outbreak can be found here.

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

  • Previous experience with cannabis or other drugs
  • Biology (e.g., genes)
  • Sex (e.g., women may experience more dizziness after using cannabis compared to men11)
  • How the drug is taken (e.g., consuming edibles or products with high tetrahydrocannabinol [THC] concentration can have delayed or unpredictable effects and increases the risk of overdose or poisoning1)
  • How much of the drug is used
  • How often it is used
  • If it is used in combination with other substances (using cannabis with alcohol or other drugs could lead to increased risk of harm, especially with unknown drug-to-drug interactions1)

The cannabis plant has compounds that may help symptoms for some health problems.1 While more states are making it legal to use the plant as medicine for certain conditions, scientists are still learning the ways that cannabis may help or harm people. For example, smoked cannabis may damage your lungs and respiratory system.1

Certain compounds in cannabis products may affect your brain or body in harmful ways. In addition, no federal standards have been implemented for the quality and safety of cannabis products sold in state-based medical cannabis dispensaries. These products are not approved by the Food and Drug Administration (FDA).

Research on the medical use of cannabis is still in early stages, and much remains unknown about the plant and how it interacts with the body. Currently, the FDA has approved one plant-based cannabis drug (Epidiolex), which contains purified cannabidiol (CBD) from the cannabis plant. The drug 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 tuberous sclerosis complex, a rare genetic disorder that causes benign tumors to form in many parts of the body.

The FDA has also approved two medicines (dronabinol [brand names: Marinol and Syndros] and nabilone [brand name: Cesamet]) made from a synthetic or lab-made chemical that mimics tetrahydrocannabinol (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).

Yes. Research suggests that 3 in 10 people who use cannabis may have some form of cannabis use disorder.12 Some signs and symptoms of cannabis use disorder include trying but failing to quit using cannabis or giving up important activities with friends and family in favor of using cannabis.13 For people who begin using cannabis before the age of 18 and who use cannabis often (daily/near daily), the risk of developing cannabis use disorder is even greater.14

In addition, the concentration or strength of tetrahydrocannabinol (THC) in cannabis products is increasing,151617 and daily or near daily use of cannabis is increasing,18 both of which could make addiction and other health consequences more likely.

For more information visit CDC's section on addiction or the National Institute on Drug Abuse's pages on addiction science and cannabis.

The signs that someone might have cannabis use disorder are:13

  • Using more cannabis than intended
  • Trying but failing to quit using cannabis
  • Spending a lot of time using cannabis
  • Craving cannabis
  • Using cannabis even when it causes problems at home, school, or work
  • Giving up important activities with friends and family in favor of using cannabis
  • Using cannabis in high-risk situations, such as driving a car
  • Continuing to use cannabis despite physical or psychological problems
  • Needing to use more cannabis to get the same high
  • Experiencing symptoms when stopping cannabis use

People with cannabis use disorder, compared to those who use cannabis but do not have cannabis use disorder, are at a greater risk for negative consequences, such as problems with attention, memory, and learning. Please visit the National Institute on Drug Abuse to learn more about addiction and available treatments.

While a fatal overdose caused solely by cannabis is unlikely, cannabis is not harmless. The signs of using too much cannabis are similar to the typical effects of using cannabis but more severe. These signs may include:1

  • extreme confusion
  • anxiety
  • paranoia
  • panic
  • fast heart rate
  • delusions or hallucinations
  • increased blood pressure
  • severe nausea or vomiting

In some cases, these effects can lead to unintentional injury, such as a motor vehicle crash, fall, or poisoning. Overconsumption of cannabis can happen especially when using cannabis-infused products like edibles and beverages, since it can take up to 2 hours to feel the effects from the drug.1 Infants or young children who unintentionally ingest cannabis are more likely to require hospital admission compared to older children who ingest similar concentrations due to their smaller size and weight and increased severity of symptoms.19

Cannabis may be mixed with other substances, either known or unknown to the consumer. Using cannabis in combination with other substances may result in greater impairment than when using cannabis alone and may increase the risk of overdose.

Learn more about cannabis and potential risk of poisoning‎

If you or someone you know is showing signs that might suggest they have used too much cannabis, call a poison control center at: at 1-800-222-1222. In case of emergency, call 9-1-1.

Learn more

For more on the health risks and effects of cannabis, visit CDC's web page on cannabis and risk factors.

Using alcohol and cannabis at the same time is likely to result in greater impairment than when using either one alone.20 Greater impairment can result in greater risk of physical harm. Using cannabis and tobacco at the same time may also lead to increased exposure to harmful chemicals that could cause greater risks to the lungs and the cardiovascular system (heart and blood vessels).21 Also, cannabis may change how prescription drugs work.22 Always talk with your doctor about any medications you are taking or thinking about taking and the possible side effects when mixed with other things, such as cannabis.

Breastfeeding persons are encouraged to avoid using cannabis.23 The health effects of a breastfeeding person's use of cannabis on their infant are not yet fully known, and the available data are limited and conflicting. However, we know that chemicals from cannabis can be passed to a baby through breast milk. In addition, tetrahydrocannabinol (THC) is stored in body fat and is slowly released over time, meaning that a baby could still be exposed even after a breastfeeding person stops using cannabis.

More research about the effects of secondhand cannabis smoke is still needed. The known risks of secondhand exposure to tobacco smoke—including risks to the heart or lungs24—raise questions about whether secondhand exposure to cannabis smoke causes similar health risks. Secondhand cannabis smoke contains many of the same toxic and cancer-causing chemicals found in tobacco smoke and contains some of those chemicals in higher amounts.6

More research is needed to understand how secondhand cannabis exposure may affect children. Secondhand cannabis smoke contains tetrahydrocannabinol (THC), the chemical responsible for most of cannabis's psychological effects (or the "high"). THC can be passed to infants and children through secondhand smoke, and people exposed to secondhand cannabis smoke can experience psychoactive effects, such as feeling high.2526 Research has found a strong association between children with detectable levels of THC in their urine and living with someone who uses cannabis (e.g., a parent, relative, or caretaker).25

Children exposed to THC are potentially at risk for negative health effects. Other research shows that cannabis use during adolescence can impact the developing teenage brain and cause problems with attention, motivation, and memory,1 which raises questions of whether secondhand smoke exposure could lead to similar negative health effects in children.

The fact that cannabis is legal in some states for medical or nonmedical adult use does not mean that it is safe. Using cannabis at any age can lead to negative health consequences:

  • Using cannabis heavily (daily or near-daily) can damage your memory, attention, and learning ability. This can last a week or more after the last time cannabis was used.27
  • Using cannabis during pregnancy or while breastfeeding may harm the baby.123
  • Cannabis use has been linked to social anxiety, depression, suicide, and schizophrenia. Scientists don't yet know whether cannabis use directly causes these health issues, but it may make symptoms more severe.
  • Smoking any product, including cannabis, can damage your lungs and cardiovascular system (heart and blood vessels).6 Eating or drinking foods with cannabis can take longer to have an effect and may increase the chance of consuming too much.1 Vaping cannabis has led to lung injury and even death.10 Use of concentrates in vaping or dabbing devices may increase a number of health risks because of the concentration or strength of cannabis being used.817

Delta-8 THC is a form of THC that can be found in small quantities naturally in the cannabis plant. Delta-8 THC can also be synthetically made from cannabidiol (CBD).

Delta-8 THC is psychoactive, meaning it can be mind-altering. However, the health effects of delta-8 THC are not yet well understood. Delta-8 THC products are sold by a wide range of businesses that sell hemp, so they have the potential to be confused with hemp or CBD products that are not intoxicating. Consumers who use these products may therefore experience unexpected or increased THC intoxication.

Delta-8 THC products can be found in both adult cannabis use and hemp marketplaces, some of which operate legally under state, territorial, or tribal laws.28 Most states and territories permit full or restricted sale of hemp and hemp-derived CBD products.29 Products sold as concentrated delta-8 THC are also widely available online. In May 2022, a federal appeals court issued a ruling that delta-8 THC is not a schedule 1 substance under federal law (AK Futures LLC v. Boyd St. Distro, LLC, 35 F.4th 682 (9th Cir. 2022)). Until the federal government clarifies its position, the regulation of delta-8 THC falls under the purview of the states, with many states banning or restricting sale of these products.30

Tetrahydrocannabinolic acid, or THCA, is one of the compounds or cannabinoids found in the cannabis plant. THCA is not psychoactive. However, when THCA is exposed to heat, such as through smoking, vaping, or dabbing, it converts into THC, which is impairing and can cause psychoactive (mind-altering) effects like feeling high.

Hemp plants produce a much greater amount of THCA than THC. Total THC is listed on cannabis packaging. Most states with medical or nonmedical adult-use cannabis programs combine the amount of THC with the potential of THCA that can convert into THC to capture intoxication potential, defined as "total THC." However, many hemp businesses are selling THCA hemp flower that is not labeled with total THC. These products often have a total THC concentration of 15% to 20% when smoked or vaped; this means that consumers might have more psychoactive or mind-altering effects than they are expecting.

The 2018 Agriculture Improvement Act (Farm Bill) removed hemp from the federal Controlled Substances Act. As written, the Farm Bill defines hemp as any part of a cannabis sativa plant with no more than 0.3% of delta-9 THC (the primary form of THC found in the cannabis plant) by dry weight. It does not include delta-9 THCA (the precursor to delta-9 THC).

Synthetic cannabinoids (called spice, K2, and other names) are man-made chemicals and, despite the name, are not cannabis or cannabinoid medicines.31 Synthetic cannabinoids are manmade chemicals that are often sprayed onto dried plant material that can then be smoked or sold as liquids to use in vaping devices.

Synthetic cannabinoids are part of a group of unregulated, mind-altering drugs that attempt to produce effects similar to illegal drugs. Their effects are not fully understood and can cause dangerous health effects because of their unpredictable chemical contents.32 Once these products are identified in the illegal marketplace, they are added to the list of schedule I substances by the Drug Enforcement Administration. Schedule I substances are illegal throughout the United States and are defined as having no medical use and high potential for abuse.

Synthetic cannabinoids can 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

Cases of severe injury and death from use of synthetic cannabinoids have been reported, along with regional outbreaks when a contaminated batch enters a specific community.33 For additional questions around synthetic cannabinoids, visit the National Institute on Drug Abuse page on synthetic cannabinoids.

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

  • Call 9-1-1 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 control center at 1-800-222-1222.
  • Call your doctor.

Cannabidiol (CBD) FAQs

Cannabis is not the same thing as cannabidiol (CBD). Cannabis refers to the dried flowers, leaves, stems, and seeds of the cannabis plant. CBD is one of the many compounds, along with THC (tetrahydrocannabinol), that can be present in the cannabis plant. CBD does not cause a "high" by itself. CBD can be derived from hemp or non-hemp (marijuana) plants. Hemp is defined as any part of a cannabis plant with low amountsA of delta-9 THC (the primary form of THC found in the cannabis plant).

In 2018, the U.S. Congress passed and signed into law the Agriculture Improvement Act (2018 Farm Bill). This law removed hemp from the federal Controlled Substances Act, effectively legalizing CBD if it comes from hemp.

However, a few states have not removed hemp from their state's controlled substances acts, so legality of CBD products differs across states.

Keep Reading: About CBD

Scientists are still learning about how CBD affects the body. The U.S. Food and Drug Administration (FDA)external iconexternal icon approved Epidiolex, a medicine that contains purified CBD from cannabis plants, to help treat seizure disorders. The FDA has concluded that this drug is safe and effective for the intended use. However, other marketed uses of CBD are not FDA approved.

  1. Less than 0.3% delta-9 THC by dry weight
  1. National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: the current state of evidence and recommendations for research. Washington, DC: The National Academies Press; 2017. Accessed February 8, 2024.
  2. Schauer GL, Njai R, Grant-Lenzy AM. Modes of marijuana use – smoking, vaping, eating, and dabbing: Results from the 2016 BRFSS in 12 States. Drug Alcohol Depend. 2020;209:107900. doi: 10.1016/j.drugalcdep.2020.107900.
  3. Schauer GL, King BA, Bunnell RE, et al. Toking, vaping, and eating for health or fun: marijuana use patterns in adults, US, 2014. Am J Prev Med. 2016;50(1):1-8. doi: 10.1016/j.amepre.2015.05.027.
  4. Zhang Z, Zheng X, Zeng DD, et al. Tracking dabbing using search query surveillance: A case study in the United States. J Med Internet Res. 2016;18(9):e252. doi: 10.2196/jmir.5802.
  5. Batalla A, Bhattacharyya S, Yuecel M, et al. Structural and functional imaging studies in chronic cannabis users: a systematic review of adolescent and adult findings. PloS One. 2013;8(2):e55821. doi: 10.1371/journal.pone.0055821
  6. Moir D, Rickert WS, Levasseur G, et al. A comparison of mainstream and sidestream marijuana and tobacco cigarette smoke produced under two machine smoking conditions. Chem Res Toxicol. 2008;21(2):494-502. doi: 10.1021/tx700275p.
  7. Raber JC, Elzinga S, Kaplan C. Understanding dabs: contamination concerns of cannabis concentrates and cannabinoid transfer during the act of dabbing. J Toxicol Sci. 2015;40(6):797-803. doi: 10.2131/jts.40.797.
  8. McLaren J, Swift W, Dillon P, et al. Cannabis potency and contamination: a review of the literature. Addiction 2008; 103: 1100–1109. doi: 10.1111/j.1360-0443.2008.02230.x.
  9. Compton WM, Grant BF, Colliver JD, et al. Prevalence of marijuana use disorders in the United States: 1991-1992 and 2001-2002. JAMA. 2004;291(17):2114-2121. doi: 10.1001/jama.291.17.2114.
  10. Krishnasamy VP, Hallowell BD, Ko JY, et al. Update: characteristics of a nationwide outbreak of e-cigarette, or vaping, product use–associated lung injury—United States, August 2019–January 2020. MMWR Morb Mortal Wkly Rep. 2020;69(3):90-94. doi: 10.15585/mmwr.mm6903e2.
  11. Fattore L, Fratta W. How important are sex differences in cannabinoid action? Br J Pharmacol. 2010;160(3):544-548. doi: 10.1111/j.1476-5381.2010.00776.x
  12. Hasin DS, Saha TD, Kerridge BT, et al. Prevalence of marijuana use disorders in the United States between 2001-2002 and 2012-2013. JAMA Psychiatry. 2015;72(12):1235-1242. doi: 10.1001/jamapsychiatry.2015.1858.
  13. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders (5th ed). Washington, DC; 2013.
  14. Winters KC, Lee C-YS. Likelihood of developing an alcohol and cannabis use disorder during youth: association with recent use and age. Drug Alcohol Depend. 2008;92(1-3):239-247. doi: 10.1016/j.drugalcdep.2007.08.005.
  15. Chandra S, Radwan MM, Majumdar CG, et al. New trends in cannabis potency in USA and Europe during the last decade (2008-2017). Eur Arch Psychiatry Clin Neurosci. 2019;269(1):5-15. doi: 10.1007/s00406-019-00983-5.
  16. Cash MC, Cunnane K, Fan C, et al. Mapping cannabis potency in medical and recreational programs in the United States. PloS One. 2020;15(3):e0230167. doi: 10.1371/journal.pone.0230167.
  17. Bidwell LC, York Williams SL, Mueller RL, et al. Exploring cannabis concentrates on the legal market: User profiles, product strength, and health-related outcomes. Addict Behav Rep. 2018;8:102-106. doi: 10.1016/j.abrep.2018.08.004.
  18. Mauro PM, Carliner H, Brown QL, et al. Age differences in daily and nondaily cannabis use in the United States, 2002-2014. J Stud Alcohol Drugs. 2018;79(3):423-431. Doi: 10.15288/jsad.2018.79.423.
  19. Wang GS, Le Lait M-C, Deakyne SJ, et al. Unintentional pediatric exposures to marijuana in Colorado, 2009-2015. JAMA Pediatr. 2016;170(9):e160971-e160971. doi: 10.1001/jamapediatrics.2016.0971.
  20. Yurasek AM, Aston ER, Metrik J. Co-use of alcohol and cannabis: A review. Curr Addict Rep. 2017;4(2):184-193. doi: 10.1007/s40429-017-0149-8.
  21. Meier E, Hatsukami DK. A review of the additive health risk of cannabis and tobacco co-use. Drug Alcohol Depend. 2016;166:6-12. doi: 10.1016/j.drugalcdep.2016.07.013.
  22. Antoniou T, Bodkin J, Ho JM. Drug interactions with cannabinoids. CMAJ. 2020;192(9):E206. doi: 10.1503/cmaj.191097.
  23. Ryan SA, Ammerman SD, O'Connor ME. Marijuana use during pregnancy and breastfeeding: implications for neonatal and childhood outcomes. Pediatrics. 2018;142(3):e20181889. doi: 10.1542/peds.2018-1889.
  24. Alberg AJ, Shopland DR, Cummings KM. The 2014 Surgeon General’s report: commemorating the 50th Anniversary of the 1964 Report of the Advisory Committee to the US Surgeon General and updating the evidence on the health consequences of cigarette smokingexternal icon. American Journal of Epidemiology. 2014;179(4):403-412.
  25. Wilson KM, Torok MR, Wei B, et al. Detecting biomarkers of secondhand marijuana smoke in young children. Pediatric Research. 2017;81(4):589-592.
  26. Cone EJ, Bigelow GE, Herrmann ES, et al. Nonsmoker exposure to secondhand cannabis smoke. III. Oral fluid and blood drug concentrations and corresponding subjective effects. J Anal Toxicol 2015;39:497–509.
  27. Solowij N, Battisti R. The chronic effects of cannabis on memory in humans: A review. Curr Drug Abuse Rev 2008;1(1):81-98. doi: 10.2174/1874473710801010081.
  28. Brightfield Group. What's the Fate of Delta-8? Consumer, Product, and Regulatory Trends. Accessed February 12, 2024.
  29. National Conference of State Legislatures. State Industrial Hemp Statutes. 2022. Accessed February 12, 2024.
  30. Public Health Law Center. What's the deal with Delta-8 THC? 2022. Accessed February 12, 2024.
  31. Gurney S, Scott K, Kacinko S, et al. Pharmacology, toxicology, and adverse effects of synthetic cannabinoid drugs. Forensic Sci Rev. 2014;26(1):53-78.
  32. Trecki J, Gerona RR, Schwartz MD. Synthetic cannabinoid-related illnesses and deaths. N Engl J Med. 2015;373(2):103-107. doi: 10.1056/NEJMp1505328.
  33. Roehler DR, Hoots BE, Vivolo-Kantor AM. Regional trends in suspected synthetic cannabinoid exposure from January 2016 to September 2019 in the United States. Drug Alcohol Depend. 2020;207:107810. doi: 10.1016/j.drugalcdep.2019.107810.