Health Topics

Cannabis (Marijuana)

Cannabis (also known as marijuana, pot, weed, grass, ganga etc.), is a substance derived from the hemp plant. It comes in the form of dried plant leaves, hashish (dried resin from plant leaves) or oil (boiled resin). Cannabis can be smoked, vaped, or ingested in the form of food or drink. There are more than 400 chemicals in cannabis. THC is the chemical in cannabis known to be psychoactive. The THC content in Cannabis is far more potent than it was in the past. Higher potency can result in more harmful effects for those who use it. (Source: PROPEL

Cannabis for medical purposes

If you think you need cannabis for medical purposes, please see your health care provider. Cannabis grown for medical purposes can be quite different from recreational cannabis. Medical cannabis also has different rules than recreational cannabis.

Learn more about accessing cannabis for medical purposes

Cannabis youth poster with a turtle

Cannabis (Marijuana, Weed, Pot) & Youth

Some Youth may think cannabis is harmless, but the opposite is true. The brain continues to develop until the age of 25. Because of this, people who use cannabis at a young age are at a higher risk for more long-term effects.

Learn more about cannabis’ effect on youth


The effects of cannabis depend on a number of factors such as: how much was used, cannabis potency, how often use occurs, how it was consumed, age, mood and environment, physical and mental health, and use of other substances at the same time (e.g. alcohol). (Source: CAMH)

Side effects of cannabis may include:

  • Feeling relaxed and happy
  • Increased anxiety or paranoia
  • Increased drowsiness or restlessness
  • Decreased ability to think and make decisions
  • Decreased ability to concentrate and remember
  • Slower reaction time
  • Poor driving performance
  • Increased appetite
  • (Source: Health Canada and CAMH

Long-term effects may include:

  • Impaired attention and memory
  • Impaired ability to think and make decisions
  • Breathing problems such as bronchitis (if cannabis is smoked)
  • Earlier onset of schizophrenia for people at high risk of developing schizophrenia
  • Physical dependence or addiction
  • (Source: CAMH and CCSA)

The Centre for Addiction and Mental Health (CAMH) has developed recommendations to reduce potential negative health effects including not using cannabis.

But, if you choose to use cannabis:

  • Delay cannabis use
  • Know what you’re using and choose lower-risk, less potent (lower THC), cannabis products
  • Don’t use synthetic , or man-made, versions of cannabis (e.g. K2 or Spice)
  • Avoid smoking cannabis – choose something safer like vaporizers or edibles
  • Avoid ‘deep inhalation’ or ‘breath-holding’
  • Limit and reduce how often you use cannabis
  • Don’t use cannabis and drive, or operate other machinery (wait at least 6 hours after using cannabis to drive)
  • Avoid combining risks listed above
  • Don’t use cannabis if you are at risk for mental health problems or are pregnant

Find out more about the explanations of these guidelines

Is cannabis addictive?
Yes, cannabis can be addictive. Youth who use cannabis heavily (daily or nearly daily) are at increased risk of dependence; dependence is characterized by psychological and physical symptoms of withdrawal (agitation, irritability, difficulty sleeping, lack of appetite, anxiety, headache, etc.)

What are the health effects of cannabis smoke?
There is no safe way to inhale cannabis. Smoke is smoke and it is dangerous to lung health. Cannabis smoke has thousands of chemicals in it and studies have shown that this smoke is similar to tobacco smoke, containing many of the same cancer causing substance and toxic chemicals. Find out more about the effects of second hand cannabis smoke.

What are the effects of cannabis on pregnancy and breastfeeding?
There is no known safe amount of cannabis use in pregnancy and when breastfeeding (source: Best Start). Find out more about cannabis and other drugs during pregnancy.

Can I drive after using cannabis?
Cannabis use can result in impaired driving. Find out more about impaired driving.

Is cannabis legal?
Yes. Non-medical cannabis became legal in Canada on October 17 2018, for adults age 19 and over.

If cannabis is legal does this mean it is safe?
No, just because something is legal, does not mean it is safe. Cigarettes are an example of a legal substance that is harmful to your health. Learn more about common myths related to cannabis, or check out the facts.

How much cannabis is legally allowed in public?
Individuals in Ontario who are 19 years and older are allowed to:

  • Possess up to 30 grams of legal dried cannabis or equivalent in non-dried form
  • Share up to 30 grams of legal cannabis with other adults (19 years and older)
  • Buy dried or fresh cannabis and cannabis oil from a provincially licensed retailer

Learn more about cannabis in Ontario and legalization

What are the risks of using cannabis with tobacco or alcohol?
Using cannabis with tobacco increases health harms. Smoke from cannabis has been shown to have many of the same toxic chemicals as tobacco such as fine particles, heavy metals and carbon monoxide. Using cannabis with alcohol also increases health harms and can result in extreme anxiety, nausea, vomiting and fainting.

How much cannabis can be grown at home?
People who are 19 years and older may grow up to 4 cannabis plants per household (not per person)

What are edibles?
Cannabis edibles are food or drink items made with cannabis or cannabis oils. People who are 19 years and older may use cannabis edibles as an alternative to smoking or vaping cannabis.

Are edibles legal?
The federal government amended the Cannabis Act on October 17, 2019 to allow the legal sale of cannabis edibles.

Where can I legally buy cannabis?
The only place to legally buy cannabis in Ontario until retail stores are established is online from the Ontario Cannabis Store

Learn more about cannabis in Ontario and legalization

Where can I smoke or vape cannabis?
 The rules for where you can and cannot smoke cannabis are the same as the rules that apply to tobacco. More information about where you can and cannot smoke or vape can be found on the City of Hamilton’s webpage for Tobacco and E-cigarettes

Where can I report smoking and vaping in public places or workplaces?
If you have questions about the law or you want to report smoking or vaping in a public place or workplace:

More information about the Smoke-Free Ontario Act can be found on our City’s website.

What can I do about smoke in my home?
View more information about smoke in your home.