Every method of cannabis use carries its own health risks. This page presents the known risks for the following methods:
The risks associated with the use of substances such as cannabis can be explained by the law of effect. Since each person uses cannabis at different frequencies, reacts differently and since the THC concentration varies depending on the product, it is difficult to predict with certainty the intensity and duration of the effects and the possible side effects.
In general, frequent, intense and long-term cannabis use increases the health risks. Using products with a high THC content is also known to increase the risks associated with mental health and cognitive abilities. For more information about the general risks of using cannabis, go to the page Health Risks of Cannabis Use.
If you are using or would like to use cannabis, visit the Lower-Risk Use page. It contains information that will help you make informed choices to reduce the risks that using this substance may have for you and people around you.
It is mainly the dried flowers, resin and some extracts of cannabis that can be smoked. As with tobacco, cannabis smoke irritates the airway and can cause severe coughing spells. Smoke from cannabis products contains toxins similar to those found in tobacco. It can promote the development of lung diseases, such as chronic bronchitis.
Some pipes (bongs) have a water reservoir that the smoke enters before it is inhaled. Some users believe that the water filters the toxins in the smoke, which has not been proven. The water cools the smoke and gives it a smoother feel. However, it does not reduce the risks associated with this method of use.
At this time, very little information is available on the health risks of secondhand cannabis smoke. Several questions remain unanswered. As a precaution, since the composition of secondhand smoke is similar to that of tobacco, avoid exposing people around you to secondhand cannabis smoke. See the section Protect your lungs and those of people around you, which provides tips on how to reduce the risks associated with smoking cannabis.
Inhaling aerosols produced by vaporizing cannabis is mainly done with the dried flowers and some forms of extracts of cannabis. Although this method of use may be safer since there is virtually no combustion, the information available does not indicate that this is a preferred method of use. “Virtually no combustion” means that the dried cannabis or a cannabis extract is heated to a temperature below the combustion temperature of the product. An aerosol containing the active ingredients is produced and inhaled. Since the cannabis is heated to a temperature below the combustion point, fewer toxic by-products are released into the aerosol compared with combustion of the product when smoked.
Some people vaporize the dried flowers or concentrated cannabis extracts using a technique known as dabbing. The technique involves higher vaporization temperatures. Substances harmful to lung health are released. Dabbing is also sometimes associated with severe pulmonary disease.
The main cannabis extracts used for dabbing contain a very high concentration of THC. Rapid vaporization of cannabis can lead to the full dose of THC being consumed in a short period of time or even in a single inhalation. This practice can lead to overdose or unpleasant side effects such as anxiety, paranoia, disorientation, nausea and vomiting.
Dabbing is likely to increase the risk of developing cannabis tolerance and dependence, since it involves inhaling high doses of THC in a short period of time. People who use concentrated cannabis extracts report more symptoms of cannabis use disorder, dependence and withdrawal than people who use other forms.
The term vaping is sometimes used to encompass both dabbing and vaporizing, but vaping is a different method of use.
The known risks of vaping cannabis are mainly related to the THC concentration and the possibility of developing a lung disease.
Vaping products often contain a high concentration of THC. This means they can cause severe side effects and increase the risk of developing dependence or a mental health disorder. Vaping is also associated with a risk of developing a severe pulmonary disease. The exact cause of this risk is not yet known. For more information, see the warning against vaping cannabis (in French only) on the website of the Ministère de la Santé et des Services sociaux.
Little is known about the other risks associated with vaping cannabis. Like any substance or electronic device, there are risks associated with handling vaping products. For instance, they are associated with accidental ingestion by youths. There is also a risk of injury for the person vaping if the electronic vaping device malfunctions, particularly if it explodes.
Ingesting cannabis mainly refers to edible products, such as oils, nanoemulsions, i.e., extracts that dissolve in water, food and beverages. Unlike the effects of smoking cannabis, which are felt within minutes of inhaling, it can take 30 to 60 minutes or even longer to feel the effects of edible products. A person who does not feel the effects may be tempted to take another dose, resulting in an overdose. In an overdose, the person may experience anxiety, paranoia, disorientation, nausea and even vomiting.
Edible cannabis products can look and taste the same as conventional food products, which can lead to accidental ingestion. Children are particularly at risk in these situations.
See the tips on consuming edible cannabis products to avoid adverse effects.
Little is known about the risks associated with using topical cannabis products, for example on the skin, nails or hair. Very little information is available on this method of use.
The most likely risk is unintentional ingestion by children, which can lead to overdose and hospitalization. An ingredient in the product used may also cause an allergic skin reaction.
MINISTÈRE DE LA SANTÉ ET DES SERVICES SOCIAUX. Law of effect.
FISCHER, Benedikt and al. Lower-Risk Cannabis Use Guidelines: A Comprehensive Update of Evidence and Recommendations. American Journal of Public Health, vol. 107, no 8, 2017, p. 1-12.
HINES, Lindsey A. and al. Association of High-Potency Cannabis Use With Mental Health and Substance Use in Adolescence. JAMA Psychiatry, vol. 77, no 10, 2020, p. 1044–1051.
HALL, Wayne and Louisa DAGENHARDT. High potency cannabis: a risk factor for dependence, poor psychosocial outcomes, and psychosis. 2015, BMJ 350, h1205.
FREEMAN, T.P. and A.R. WINSTOCK. Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychological Medicine, vol. 45, 2015, p. 3181-3189.
TASHKIN, Donald P. Effects of marijuana smoking on the lung. Annals of the American Thoracic Society, vol. 10, no 3, 2013, p. 239-247.
POMAHACOVA B., F. VAN DER KOOY F and R. VERPOORTE. Cannabis smoke condensate III: the cannabinoid content of vaporised Cannabis sativa. Inhalation Toxicology, vol. 21, no 13, 2009, p. 1108-1112.
NEWMEYER, Matthew N. and al. Subjective and physiological effects, and expired carbon monoxide concentrations in frequent and occasional cannabis smokers following smoked, vaporized, and oral cannabis administration. Drug and Alcohol Dependence, vol. 175, 2017, p. 67-76.
ABRAMS, D.I. and al. Vaporization as a smokeless cannabis delivery system: a pilot study. Clinical Pharmacology & Therapeutics, vol. 82, no 5, 2007, p. 572-578.
VAN DAM, N.T. and M. EARLEYWINE. Pulmonary function in cannabis users: Support for a clinical trial of the vaporizer. International Journal of Drug Policy, vol. 21, no 6, 2010, p. 511-513.
LOFLIN, Mallory and Mitch EARLEYWINE. A new method of cannabis ingestion: the dangers of dabs? Addictive Behaviors, vol. 39, 2014, p. 1430-1433.
RABER Jeffrey C., Sytze ELZINGA S. and Charles KAPLAN. Understanding dabs: contamination concerns of cannabis concentrates and cannabinoid transfer during the act of dabbing. The Journal of Toxicological Sciences, vol. 40, no 6, 2015, p.797-803.
ANDERSON, Ryan P. and Katie ZECHAR. Lung injury from inhaling butane hash oil mimics pneumonia. Respiratory Medicine Case Reports, vol. 26, 2019, p. 171-173.
FREEMAN, T.P. and A.R. WINSTOCK. Examining the profile of high-potency cannabis and its association with severity of cannabis dependence. Psychological Medicine, vol. 45, no 15, 2015, p. 3181-3189.
CINNAMON BIDWELL, L. and al. Exploring cannabis concentrates on the legal market: User profiles, product strength, and health-related outcomes. Addictive Behaviors Reports, vol. 8, 2018, p. 102-106.
MEIER, M.H. Associations between butane hash oil use and cannabis-related problems. Drug Alcohol Depend, vol. 179, 2017 p. 25-31.
CAULKINS, Jonathan P. and al. Big data on a big new market: Insights from Washington State's legal cannabis market. International Journal of Drug Policy, vol. 57, 2018, p.86-94.
DAVENPORT, Steven. Price and product variation in Washington’s recreational cannabis market. International Journal of Drug Policy, 102547. doi:10.1016/j.drugpo.2019.08.004.
CHADI, Nicholas, MD MPH, Claudia MINATO and Richard STANWICK, MD MSc. Cannabis vaping: Understanding the health risks of a rapidly emerging trend, Paediatrics & Child Health, vol. 25, Issue Supplement_1, 2020, p. S16–S20.
CHADI, Nicholas and al. Vaping-related injury and illness among Canadian children and adolescents: a one-time survey of paediatric providers. BMJ Paediatrics Open, 2020;4:e000840.
GOUVERNEMENT DU CANADA. Vaping-associated lung illness.
CENTERS FOR DISEASE CONTROL AND PREVENTION. Outbreak of Lung Injury Associated with E-cigarette Use or Vaping.
Last update: February 26, 2021 3:14 PM