Cannabis health effects

Cannabis and your health

Cannabis contains substances that affect the brain and body, including delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD). THC causes the intoxicating effects of cannabis. CBD is not intoxicating but can still have effects on the brain.

Find resources on substance use and addiction.

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The short-term effects of cannabis use

Everyone's response to cannabis differs and can vary from one time to the next.

When cannabis is used, it can:

The long-term risks of cannabis use

Using cannabis frequently (daily or almost daily) and over a long time (several months or years) can:

The effects of cannabis on young people's health

Cannabis affects the same biological system in the brain that is responsible for brain development.Footnote 11

Youth and young adults are more likely to experience harms from cannabis because their brains develop until about age 25. The earlier you start consuming cannabis, the more harm it can do.Footnote 11

Starting as a teen, consuming frequently (daily or near daily) and over a long time (several months or years) increases the risk of mental health problems. These problems include dependence and disorders related to anxiety and depression.Footnote 11

Frequent use of cannabis over a long time can also harm important aspects of your thinking, like learning and memory. Stopping use can help improve these deficits. However, some of these harms may persist for months or years, or may not be fully reversible.Footnote 12 Footnote 13 Footnote 14

Lowering your risks when consuming cannabis

There are risks associated with cannabis use. The best way to protect your health is to avoid using cannabis or cannabis products completely.

Cannabis can be consumed in different ways. Two common ways are:

Each way carries different health and safety risks.

Everyone's response to cannabis is different, depending on:

Everyone's response to cannabis can also differ from one time to the next.

Research suggests that there are ways to reduce the risks:

For more information, please see the lower-risk cannabis use guidelines developed by Canadian experts in mental health and addiction.

The effects of cannabis on pregnancy and breastfeeding

Avoid cannabis completely if you are pregnant or breastfeeding. Substances in cannabis are transferred from the mother to child and can harm your unborn or newborn baby.

There may also be other health risks associated with cannabis use during pregnancy and breastfeeding.Footnote 24Footnote 25

If you have questions, visit your health care provider.

Cannabis for medical purposes

Some people use cannabis for their health problems. Deciding if cannabis is appropriate to treat your symptoms is best done in discussion with a health care provider.

To help you and your health care provider make informed decisions about the potential benefits and risks, we have published information on using cannabis for medical purposes.

Cannabis addiction

Cannabis addiction is real, although the risk of addiction is lower than it is for other substances such as:

Using cannabis frequently can lead to a pattern of problematic use or use disorder. This can result in dependence or addiction.

Experiencing a cannabis addiction can cause serious harm to your:

What we know:

Quitting is not always easy. If you are struggling with your cannabis use, you can:

Know the signs of cannabis addiction and where to get help.

Cannabis poisoning

Accidentally consuming or consuming too much cannabis at a time can lead to temporary adverse effects, also known as cannabis poisoning. Cannabis poisoning is not generally known to be fatal. It can, however, be very unpleasant and potentially dangerous, sometimes requiring emergency medical attention and, in some cases, hospitalization. Children and pets are at greater risk of cannabis poisoning.

SymptomsFootnote 18Footnote 19Footnote 26 can include:

The higher the THC content in a product, the higher the likelihood of experiencing adverse effects/poisoning, especially if you are a first-time or inexperienced user.

It is also easier to be poisoned when ingesting (eating or drinking) cannabis compared to inhaling cannabis (smoking or vaping). This is because some of these products may be confused with similar non-cannabis products. It can also take much longer to feel the effects. The result is that people consume more before they feel the full effects.

When eating or drinking cannabis, it can take up to::Footnote 15Footnote 17Footnote 18Footnote 19Footnote 20Footnote 21

Store all cannabis products safely, keeping them out of reach of children, youth and pets. This is particularly important for edible cannabis, which may be mistaken for regular food or drinks.

If you've consumed cannabis and are experiencing particularly unpleasant or harmful effects:

Note: If you have consumed cannabis, don't drive. There is no guidance to drivers about:


Footnote 1

Hartman RL, Huestis MA. Cannabis effects on driving skills. Clin Chem 2013 Mar;59(3):478-92.

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World Health Organization (WHO). The health and social effects of nonmedical cannabis use.

World Health Organization (WHO). The health and social effects of nonmedical cannabis use.

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Footnote 3

Martinasek MP, McGrogan JB, Maysonet A. A systematic review of the respiratory effects of inhalational marijuana. Respir Care 2016 Nov;61(11):1543-51.

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Footnote 4

Gobbi, G., Atkin, T., Zytynski, T., Wang, S., Askari, S., Boruff, J.,... & Mayo, N. (2019). Association of cannabis use in adolescence and risk of depression, anxiety, and suicidality in young adulthood: a systematic review and meta-analysis. JAMA psychiatry.

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Footnote 5

Mammen, G., Rueda, S., Roerecke, M., Bonato, S., Lev-Ran, S., & Rehm, J. (2018). Association of Cannabis With Long-Term Clinical Symptoms in Anxiety and Mood Disorders: A Systematic Review of Prospective Studies. The Journal of clinical psychiatry, 79(4).

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Footnote 6

Gorelick, S. A., & Hermann, R. (2017). Cannabis use and disorder: Epidemiology, comorbidity, health consequences, and medico-legal status. UpToDate. September, 2-150.

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Footnote 7

Pierre, J. M. (2017). Risks of increasingly potent Cannabis: the joint effects of potency and frequency: as THC levels rise, the risk of psychosis, cognitive deficits, and structural brain changes increases. Current Psychiatry, 16(2), 14-21

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Footnote 8

Meier MH. Associations between butane hash oil use and cannabis-related problems. Drug and Alcohol Dependence. 2017;179:25-31.

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Footnote 9

Freeman, T. P., & Winstock, A. R. (2015). Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychological medicine, 45(15), 3181-3189.

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Footnote 10

Moitra, E., Anderson, B. J., & Stein, M. D. (2016). Reductions in cannabis use are associated with mood improvement in female emerging adults. Depression and anxiety, 33(4), 332-338.

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Footnote 11

Chadwick B, Miller ML, Hurd YL. Cannabis use during adolescent development: Susceptibility to psychiatric illness. Front Psychiatry 2013 Oct 14;4:129.

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Footnote 12

Rathee, S., & Shyam, R. (2018). Effect of Abstinence on Memory Functions in Cannabis Users. Journal of Psychosocial Research, 13(2), 443-451.

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Footnote 13

Schuster, R. M., Gilman, J., Schoenfeld, D., Evenden, J., Hareli, M., Ulysse, C.,... & Evins, A. E. (2018). One Month of Cannabis Abstinence in Adolescents and Young Adults Is Associated With Improved Memory. The Journal of clinical psychiatry, 79(6).

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Footnote 14

Meier, M. H., Caspi, A., Ambler, A., Harrington, H., Houts, R., Keefe, R. S.,... & Moffitt, T. E. (2012). Persistent cannabis users show neuropsychological decline from childhood to midlife. Proceedings of the National Academy of Sciences, 109(40), E2657-E2664.

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Footnote 15

National Academies of Sciences, Engineering, and Medicine. The health effects of cannabis and cannabinoids: The current state of evidence and recommendations for research. Washington, D.C.: National Academies Press; 2017.

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Footnote 16

Volkow ND, Baler RD, Compton WM, Weiss SR. Adverse health effects of marijuana use. N Engl J Med 2014 Jun 5;370(23):2219-27.

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Footnote 17

Kosa, K. M., Giombi, K. C., Rains, C. B., & Cates, S. C. (2017). Consumer use and understanding of labelling information on edible marijuana products sold for recreational use in the states of Colorado and Washington. International Journal of Drug Policy, 43, 57-66.

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Footnote 18

Hudak, M., Severn, D., & Nordstrom, K. (2015). Edible cannabis-induced psychosis: intoxication and beyond. American Journal of Psychiatry, 172(9), 911-912.

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Footnote 19

Cone, E.J., Johnson, R.E., Paul, B.D., Mell, L.D., Mitchell, J., 1988. Marijuana-laced brownies: behavioral effects, physiologic effects, and urinalysis in humans following ingestion. J. Anal. Toxicol. 12, 169-175

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Footnote 20

Barrus DG, Capogrossi KL, Cates SC, Gourdet CK, Peiper NC, Novak SP, Lefever TW, Wiley JL (2016). Tasty THC: Promises and Challenges of Cannabis Edibles. Methods Rep RTI Press. 2016 Nov;2016. doi: 10.3768/rtipress.2016.op.0035.1611.

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Footnote 21

Chen, P., & Rogers, M. A. (2019). Opportunities and Challenges in Developing Orally-Administered Cannabis Edibles. Current Opinion in Food Science.

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Footnote 22

Schoeler T, Petros N, Di Forti M, Klamerus E, Foglia E, Ajnakina O, Gayer-Anderson C, Colizzi M, Quattrone D, Behlke I, Shetty S, McGuire P, David AS, Murray R, Bhattacharyya S (2016). Effects of continuation, frequency, and type of cannabis use on relapse in the first 2 years after onset of psychosis: an observational study. Lancet Psychiatry. 2016 Oct;3(10):947-953. doi: 10.1016/S2215-0366(16)30188-2. Epub 2016 Aug 23.

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Footnote 23

Schoeler T, Monk A, Sami MB, Klamerus E, Foglia E, Brown R, Camuri G, Altamura AC, Murray R, Bhattacharyya S (2016). Continued versus discontinued cannabis use in patients with psychosis: a systematic review and meta-analysis. Lancet Psychiatry. 2016 Mar;3(3):215-25. doi: 10.1016/S2215-0366(15)00363-6. Epub 2016 Jan 15.

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Footnote 24

Gunn JK, Rosales CB, Center KE, Nuñez A, Gibson SJ, Christ C, Ehiri JE (2016). Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis. BMJ Open. 2016 Apr 5;6(4):e009986. doi: 10.1136/bmjopen-2015-009986.

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Footnote 25

Grant KS, Petroff R, Isoherranen N, Stella N, Burbacher TM (2018). Cannabis use during pregnancy: Pharmacokinetics and effects on child development. Pharmacol Ther. 2018 Feb;182:133-151. doi: 10.1016/j.pharmthera.2017.08.014. Epub 2017 Aug 25.

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Footnote 26

Noble MJ, Hedberg K, Hendrickson RG (2019). Acute cannabis toxicity. Clin Toxicol (Phila). 2019 Jan 24:1-8. doi: 10.1080/15563650.2018.1548708. [Epub ahead of print]

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