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Health Effects

What is cannabis?

  • Cannabis is a greenish or brownish material consisting of the dried flowering, fruiting tops and leaves of the Cannabis Sativa
  • Cannabis is known by many names including marijuana, weed, hash – and others.
  • Cannabis is most often smoked in a “joint”, water pipe or “bong” where the smoke is drawn through water to cool it and filter out small particles before inhaling. It can also be vaporized in an e-cigarette or consumed in edible products.

Who is using cannabis? 

According to the 2022 Canadian Cannabis Survey:

  • About 27% of all Canadians aged 16 and older have used cannabis at least once in the past year, an increase from 25% in the previous survey.
  • As in previous years, past 12-month cannabis use was highest among 20-24 year olds (50%), followed by 16-19 year olds (37%) and those 25 years and older (25%).
  • Males (30%) reported a higher percentage of cannabis use in the past year than females (25%). Reported past 12-month cannabis use increased between 2021 and 2022 among females, but was unchanged among males
  • 13% of survey respondents used cannabis exclusively for non-medical purposes, 5% used cannabis for both medical and non-medical purposes, and 4% for medical purposes only.
  • The most common method of consuming cannabis is smoking.
  • Alcohol is the most commonly used substance with cannabis.
  • The average age of starting cannabis use was 20.5 years, unchanged from 20.4 years in 2021.

High on cannabis – what does that mean?

Cannabis affects people in different ways. Symptoms of “being high” on cannabis include feeling happy, relaxed, increased sociability and heightened sensation, decreased attention span, increased heart rate, slowed reaction times, trouble with thinking and problem solving and a lack of a sense of time. Symptoms can last several hours and sometimes less enjoyable symptoms like nervousness and paranoia can be expected. These effects may be even greater when cannabis is mixed with other drugs or alcohol.

Immediate and long term health effects

By consuming cannabis, you can experience unpleasant and unwanted short and long term negative effects on your brain and body, some of which may not be reversible.

Short-term effects on the brain and body include:

  • Confusion
  • Sleepiness
  • Impaired ability to remember, concentrate, pay attention
  • Anxiety, fear or panic
  • Psychotic episodes including paranoia, delusions or hallucinations
  • Damaged blood vessels caused by the smoke
  • Decreased blood pressure, causing fainting
  • Increased heart rate, which can be dangerous for people with heart conditions and could increase the risk of heart attack

Long-term effects on the brain and body include:

  • Harm to memory, concentration, IQ and the ability to think and make decisions, which may not be reversible once cannabis use stops
  • Cannabis smoke contains many of the same cancer-causing ingredients as tobacco smoke—making airways more susceptible to respiratory problems

Increased risk to lung health including bronchitis, lung infections, chronic cough, increased mucus build up in the throat

Lower your risk by adhering to Canada’s Lower Risk Cannabis Use Guidelines

Follow the links to find out more about how cannabis can affect your short and long term health

Short and long term effects on the brain and body
Health Effects of cannabis use
Clearing the Smoke on Cannabis-Report


Continued, frequent, and heavy cannabis use can cause physical dependence and lead to addiction.

Problematic behaviours can include some or all of the following:

  • Failing to fulfill major duties at work or school
  • Giving up on social, occupational or recreational activities
  • Being unable to reduce or control cannabis use

If you or someone you know is struggling from a cannabis addiction, help is available. Refer to the “Community Resources” page on this site.

Cannabis Use and Pregnancy

  • Cannabis is the most commonly used illicit drug during pregnancy.
  • Prenatal exposure to cannabis has adverse effects on cognitive development and academic achievement including attention deficits, increased hyperactivity and impulsivity.
  • There is emerging evidence of an increased likelihood of smoking, substance abuse and delinquency among adolescents who were prenatally exposed to cannabis.
  • THC (the active ingredient in cannabis) can be passed to the baby through breastfeeding and affect the baby’s motor development.
  • Second hand cannabis smoke can cause the same health effects for children and infants as second hand tobacco smoke.


If you are experiencing problems stopping your recreational cannabis use during pregnancy, seek help from your health care provider. Visit the links below for more information on cannabis use during pregnancy.

Clearing the Smoke on Cannabis-Maternal Cannabis Use during Pregnancy
Risks of Cannabis on Fertility, Pregnancy, Breastfeeding and Parenting
Women and Marijuana

Cannabis Use and Driving

  • There is no evidence for safe levels of cannabis use for driving.
  • Cannabis has been found to impair reaction time, visual function, concentration, short term memory and the divided attention necessary to operate a motor vehicle.
  • Among young drivers, driving after using cannabis is more prevalent than driving after drinking.
  • Recent research has found that 50% of youth surveyed, believe driving under the influence of cannabis is more socially acceptable than driving drunk.
  • Cannabis use doubles the risk of a crash and, after alcohol, cannabis is the most commonly detected substance among drivers who die in traffic crashes.
  • The percentage of Canadians fatally injured in traffic crashes who test positive for drugs exceeds that of drivers who test positive for alcohol.
  • Even a small amount of alcohol, if consumed with cannabis, can greatly decrease a person’s ability to drive safely.
  • With enhancements to drug-impaired driving laws in Ontario, police have the tools and authority to detect and arrest drivers who are impaired.

Health Canada: Don’t Drive High Campaign

Get to know the facts about cannabis and drug-impaired driving, follow the links for more information.

The Facts about Drug-Impaired Driving
Clearing the Smoke on Cannabis: Cannabis Use and Driving
Cost of Cannabis Collisions in Canada

Cannabis, Alcohol Use and Driving

The use of cannabis alone is enough to impair judgement. When mixed with alcohol the level of intoxication and impairment can be unpredictable and lead to a greater likelihood of negative physical and psychological side effects.

The use of both alcohol and cannabis before driving can greatly increase the already high risk of getting into a car accident.

Don’t drink and drive, don’t drive high.