Santé Montréal

Spotlight on cannabis

Facts about cannabis and its effects

The plant

Some of the many words used to talk about products made from this plant: cannabis

Cannabis contains over 500 organic compounds. The two main ones are :

  • THC or delta-9 tetrahydrocannabinol
    This is the main psychoactive ingredient of the drug, the one that makes you high.

  • CBD or cannabidiol
    This ingredient does not produce a high. It may influence the harms of THC. (e.g. anxiety). 
    Researchers point to CBD for its potential use in the treatment of certain diseases.

Click to enlarge illustration.

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Methods of consumption

Vapourized or vaped
Eaten or drunk
Applied on skin

High occurs within seconds or minutes and lasts up to 4 hours

Don’t mix with tobacco

High occurs within seconds or minutes and lasts up to 4 hours

Opt for vapourizing dried cannabis rather than vaping e-liquids

Very intense high occurs within seconds or minutes 
Avoid dabbing, especially if you’re new to cannabis

*Dabbing is the instant vapourization of high-concentration cannabis products.

High comes on slowly (up to 2 hours) and lasts longer (up to 12 hours)
Start with low doses of THC—2.5 mg or less—and wait until you feel the effects before taking more.
Store edibles in a safe place to prevent children and animals from accidentally eating them.

Local effect, doesn’t produce a high

In the past year in Montréal, among cannabis users 93% smoked it at least once  25% vapourized or vaped it at least once 5% dabbed it at least once 40% ate or drank it at least once  

Source: Enquête québécoise sur le cannabis (2018)

Warning – Québec’s Director of public health encourages the population not to use cannabis (or cannabinoids such as THC and CBD) vaping products, whether purchased legally or illegally.

In this context and in light of its mission of ensuring the sale of cannabis from a health protection perspective, the Director considers that the Société québécoise du cannabis (SQDC) should not sell cannabis vaping liquid until further notice. Public health authorities are monitoring the situation closely and will keep the SQDC informed of any developments.

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Forms of cannabis


Dried flowers or leaves

  • Joint, blunt, pipe, bong, vapourizers

Liquid extracts for ingestion 

  • Gel, sublingual oils (pipettes or vapourizers)

Edible products


  • Joint, blunt, pipe, bong

Liquid extracts for inhalation

  • Vape pen, vape cartridge


(Legal in Canada 17/10/19)

Solid extracts (wax, shatter) (up to  99 % THC

  • Vape pen, dab rig

Topical products

  • Creme, salve, shampoo, and others 

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Everyone reacts differently to cannabis. Several factors influence the experience:

  • a person’s physical and mental health,
  • the product used (THC and CBD levels),
  • the method of consumption
  • and the social context in which it is used.

Being under the influence of cannabis

When taken, cannabis can

  • promote a sense of well-being, relaxation and calm,
  • alter perceptions of time and space,
  • increase sociability and carefree mood,
  • heighten the senses,
  • disrupt attentiveness and memory, 
  • cause tremors,
  • impair coordination and balance.

Other physical effects: rapid heartbeat, red eyes, dry mouth and throat.

Cause accidents and injuries

Cannabis impairs the functions that are essential for driving and operating machinery. Cannabis use increases reaction times and reduces attention. These effects increase the risk of accidents.

Long-term effects

Affects mental health
Regular cannabis use (every day or almost every day) over a long period of time (several months or years) can prematurely trigger schizophrenia or other psychoses in people with personal or family histories of these mental disorders.

The risk increases in people who:

  • start using at a young age 
  • and use cannabis products with high levels of THC (e.g. shatter and wax).

Psychosis is a serious mental disorder in which people lose touch with reality. It is often characterized by delusions and hallucinations ii.

ii CCLCT. 2016. Clearing the Smoke on Cannabis.

Provokes addiction

Cannabis can lead to physical and psychological addiction in 1 out of 10 users. The risk increases in people who:

  • use several times a week or every day,
  • consume very high levels of THC,
  • and start using a young age.

Damages the lungs

Regular cannabis smokers cough more, have more secretions and can have difficulty breathing. Cannabis smoke is just as harmful as tobacco smoke and contains more tar.

Affects babies 

Cannabis use during pregnancy is linked to low birthweight babies. There is not enough proof to establish solid links between cannabis use and long-term negative effects for the child. THC also passes through breast milk. The risks of secondhand cannabis smoke are similar to those of tobacco.

Therapeutic use

Studies have shown that cannabis can effectively relieve nausea, vomiting and certain types of pain, as well as stimulate the appetite. However, cannabis isn’t always the best drug to use for those purposes.iii Talk it over with a health professional.

iii Kalant, H et Porath-Waller, A. (2016). Clearing the Smoke on Cannabis: Medical Use of Cannabis and Cannabinoids. Canadian Centre on Substance Abuse.

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Know the law

Legal cannabis is regulated by federal and provincial laws. Municipalities also have the power to impose stricter regulations. 


Legal age: 21 and over

Legal points of purchase: SQDC

Quantities allowed: 30 g personal possession and 150 g in non-public places (including second homes)

Home cultivation: prohibited

Driving: zero tolerance

No smoking or vaping cannabis in all public places.

For more information about the Cannabis Act or to file a complaint:

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Who uses cannabis in Montreal?

Cannabis use in the past 12 months, population aged 15 and over, Montreal, 2014–2015


Over 17% of Montrealers aged over 15 years revealed using cannabis in the past year.

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Last Update : 05 March 2020