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After alcohol, cannabis is the most commonly used substance in Canada.

Cannabis (also known as mary jane, hash, blunt, dab, joint) is a product of the plant cannabis sativa. The main active chemical in cannabis is THC (delta-9-tetrahydrocannabinol). THC is a psychoactive chemical that gives a high or feeling of euphoria to those who use it. Another active chemical in cannabis is CBD (cannabidiol), which is presently being studied and used for medical purposes. It does not have psychoactive properties.

Types of Cannabis

Cannabis comes in a variety of forms that can be consumed in different ways. The extent of risks and harms of cannabis use are not yet entirely clear, but research shows that cannabis use is not harmless. 

  • Dried flower – leaves and buds from the cannabis plan can be smoked or vaped.
  • Edibles – refer to food or drinks that contain active cannabinoids (THC, CBD).
  • Extracts – wax or shatter contains a high concentration of THC. 

* Higher concentrations increase the risk of experiencing mental health challenges, dependences and can change how the brain grows, affecting performance and cognitive function

  • Oils – cannabis extracts that are diluted in food-grade oil used to make edibles
  • Topicals (cream put on the skin) – usually higher in CBD and lower in THC and used for medical purposes
  • Synthetic Cannabis – also called K2 and Spice are illegal products and are stronger and more dangerous than cannabis products made from the cannabis plant. 

* Synthetic cannabis can cause seizures, irregular heartbeat, hallucinations and in rare cases, death.

Click on this link to find out more CCSA -Know your Limits with Cannabis Guide

What is the legal age to use Cannabis?

The legal minimum age in Ontario is 19 years old, to purchase, use, possess and grow cannabis. This is the same as the minimum age for the sale of tobacco and alcohol in Ontario.

Where can you buy Cannabis?

You can buy cannabis at an authorized retailer or from the online Ontario Cannabis Store.  Look for the Cannabis retail seal.  Health and safety risks are associated with cannabis obtained illegally.  The quality(potency) and purity of illegal cannabis is largely unknown and is frequently mixed with or contains pesticides, other drugs, heavy metals, moulds or fungi and other contaminants.


What are the Ontario smoking or vaping cannabis laws in public places?

The Government of Ontario prohibits smoking or vaping cannabis in:

  • Enclosed public places (inside businesses, hospitals, restaurants),
  • Enclosed workplaces,
  • Common areas of buildings, such as hallways, laundry rooms and entertainment rooms,
  • Schools and school grounds,
  • Hospital grounds,
  • Near child care centres,
  • Restaurants, bars and patios, and
  • Vehicle or boat, whether the person is a driver or passenger (any form of cannabis)

Smoking or vaping tobacco and non-tobacco substances, including cannabis, on municipal property is not allowed (City/municipal parks, arenas, recreational centers, libraries and pools).

Smoking by-laws in each municipality may have further restrictions.  Check our your municipality’s website for their smoking by-laws.

Landlords, condominium boards and co-operative housing boards may have more rules on cannabis use. Check what rules apply to your residence.

For more information see Smoking/Vaping section on our website

How much can I have in public?

You can have up to 30 grams (about one ounce) of dried cannabis or the equivalent in other forms in public.

Can I grow cannabis at home?

You can grow up to four plants per residence.  Find out what rules apply to your residence if you live in a condo, community housing or rental unit.  The health risks that come from growing at home include accidental consumption or poisoning, compromised indoor air quality due to humidity, odour and carbon monoxide, exposure to pesticides and electrical and fire hazards.

Driving and Cannabis

If you are 21 or under, a novice driver, or a commercial driver there is a zero tolerance law for impaired driving whereby you cannot have any alcohol or drugs in your system.

Older than 21? Driving a vehicle while you’re impaired by cannabis is illegal and dangerous. This includes cars, trucks, boats, snowmobiles and off-road vehicles.

You are not a safer driver when you’re high. Cannabis affects your judgment, coordination and reaction time, and increases your chances of being in a collision.

Travelling with Cannabis

Cannabis is only legal inside Canada’s borders.  It is illegal to take cannabis outside of Canada.

For more information, see the following websites: Health Canada:  Drugs, Alcohol and Travel

The flowers and leaves of a cannabis plant are used for their ability to cause euphoria, a sense of well-being, relaxation and heightened sensory however there are short term and long term risks to your brain and body.

Short term effects of cannabis use include:

  • Confusion, sleepiness (fatigue), impaired memory/concentration/attention, anxiety, and can result in psychotic episodes.
  • Increased heart rate, damaged blood vessels caused by smoke and decreased blood pressure are some of the effects on the body.

Long term effects of cannabis use develop over time with daily or near-daily use that continues over days, weeks, and months:

  • Physical and mental health problems (including psychosis)
  • Decreased cognitive functioning (memory, attention, problem solving)
  • Reproductive health issues
  • Increased risk of addiction
  • Lung health issues including bronchitis, lunch infections, and chronic cough/
  • These effects can last days to months after stopping use and some are not reversible.

Cannabis can lead to dependence.  Regular use can lead to cannabis use disorder or dependence making it hard to cut down or stop using.  Some symptoms of dependence are feeling irritable or anxious, an upset stomach, trouble sleeping, loss of appetite and sweating.

Daily or near-daily cannabis use increases the risk of dependence and can bring on or worsen disorders related to anxiety or depression. Regular use of cannabis products containing high levels of THC can increase your risk of developing psychosis, especially if you have a family history of psychosis or schizophrenia.

There is developing evidence in the use of cannibidiol (CBD) having therapeutic effects.  Patients can seek more information from their doctor or health care provider.

For more information:

Youth and Young Adults

Exposure to THC (the psycho-active component of cannabis) can have a negative and irreversible impact to the development of the adolescent brain. Regular or frequent use of cannabis (daily or near daily) has been associated with an increased risk of depression and anxiety disorders. Continued chronic cannabis use by individuals who initiate use at an early age is associated with cognitive and neuropsychological deficits, negatively impacting their future mental health. Deter or delay early onset of cannabis use until after 25 years of age is safest for brain development.

What you can do as a parent, guardian or caregiver of youth?

Preconception (Fertility), Pregnant, and Breastfeeding Persons

Studies have shown that cannabis use can affect your ability to get pregnant. Using cannabis during pregnancy causes the toxins to be carried through the mother’s blood to her fetus. Smoking reduces the supply of oxygen to the fetus. Once born, the baby may be of low birthweight, have reduced alertness and slower growth. Cannabis use during pregnancy has also been associated with longer-term developmental effects in children and adolescents, such as: decreases in: memory function, the ability to pay attention, reasoning and problem-solving skills, hyperactive behaviour and increased risk for future substance use. THC passes into the breast milk and to the baby’s fat cells and brain and can be stored for weeks. Some studies suggest that this exposure can lead to slower motor responses in baby.

More questions?  Talk to your health care practitioner to learn how to protect your health and your family’s health.

Substance Use in Pregnancy – Society of Gynecologists and Obstetricians

History of Mental Health Issues

Personal or family history of mental health problems increases the risk of dependency and of developing mental health problems.

Talk to your health care practitioner and take steps to protect your health.


Clearing the Smoke on Cannabis Highlights – Canadian Centre for Substance Abuse

Clearing the Smoke on Cannabis: Maternal Cannabis Use during Pregnancy

Cannabis use and Adolescents – Canadian Centre for Substance Abuse

Society of Gynecologists and Obstetricians

The SOGC Urges Canadians to Avoid Cannabis Use During Pregnancy and Breastfeeding

Cannabis and Canada’s Children and Youth – Canadian Pediatric Society

  1. Abstain from use
  2. Avoid early initiation of cannabis use (before age 16)
  3. Use cannabis with a low THC content and a higher CBD:THC ratio
  4. Avoid synthetics cannabinoids (“spice”)
  5. Avoid routes of administration that involve smoking combusted material (use vaporisers or edibles)
  6. Avoid deep inhalation or breath holding
  7. Avoid daily or near daily cannabis use
  8. Refrain from driving for at least 6 hours post using cannabis (there is some data to say more than 8 hours)
  9. People at higher risk for cannabis-related outcomes refrain from using it (predisposition to psychosis, substance use disorders, pregnant women with effect on fetus)
  10. Preventing high risk behaviours e.g., early onset use of high potency cannabis

Canada’s Lower-Risk Cannabis use Guidelines

Start low and go slow:

Cannabis edible products purchased through legal sources (Ontario Cannabis Store) that are ingested (eating, drinking/swallowing) can have up to 10 mg THC per package.

Start with 2.5 mg THC or less – Effects begin between 30 min to 2 hours and peak at 4 hours and could last up to 12 hours.

Cannabis products that are inhaled (smoking/vaping) have effects can be felt from seconds to minutes, peaking at 30 minutes and last for 6 hours or more.

Use products with low THC and equal or higher CBD.

Read the cannabis package – understand how to read the labels and what the information means to you on the Ottawa Public Health site.

Protect your lungs

If you vape, monitor yourself for symptoms of lung (pulmonary) illness such as cough, shortness of breath and chest pain. Seek medical attention if you have concerns about your health. Be sure to indicate to your health care professional that you currently vape, or have in the past, and what you were vaping. Only dried cannabis is legally available for use with a vaporizer.  Obtain cannabis from legal sources.  Illegal or unregulated sources have no controls for safety, quality.

Safe storage of all substances

This includes cannabis as well as tobacco, alcohol and all prescription medications.  Keep products in their original packaging, in a locked place out of reach and out of sight of children and pets.

If you or your child has accidentally consumed drugs or medication, contact the Ontario Poison Control Centre at 1-800-268-9017. Cannabis poisoning in babies and children is a medical emergency.

Symptoms of cannabis poisoning in children include:

  • Changes in mood such as confusion
  • Agitation or sleepiness
  • Changes in appetite
  • Nausea and vomiting
  • Slurred speech
  • Balance problems and difficulty breathing
  • Call 9-1-1 if your child is ill and/or has difficulty breathing.

Stick to one drug at a time.

Using more than one substance at a time can lead to unpredictable changes in how you think, feel and act.  Using cannabis in combination increases the risk of poor mental health outcomes (dependence) and can increase the strength of the psychoactive effects of cannabis.

Plan a safe ride.

The effects of cannabis can last from 6 to 12 hours.  Make sure you plan a safe ride home with a friend, public transit or a taxi. Driving – Short term effects of cannabis include feeling happy, relaxed, increased heart rate, decreased attention span, slowed reaction time, nervousness, paranoia, body tremors, distorted perception (sights, sounds, time, touch), loss of motor coordination and anxiety. These effects may be even greater when other drugs are mixed with cannabis.

Avoid sharing – why?

Try to avoid sharing joints and equipment with other people in order to reduce your risk of sharing infections (Sexually transmitted infections and respiratory infections).

Have more substance free days.

Regular use of cannabis or any substance can have negative effects on your mind and body over the short and long term.  Get involved with an activity that doesn’t involve cannabis.  Fill free time with hobbies and family and friends that make you feel good. If you used cannabis to help you feel comfortable in social situations or to cope with stress, explore new techniques and strategies. This can include breathing exercises, meditation, yoga or replacing negative self-talk with positive self-talk.

Know where to go for help.

If you are concerned about yourself or someone else, seek help from:

Signs you may need help with your cannabis or other drug use include:

  • Ignoring responsibilities at work, school, or home.
  • Giving up activities that you find important or enjoyable.
  • Using the drug more often.
  • Feeling unable to cut down or manage your use.
  • Changes in mood (e.g., feeling irritable and paranoid).
  • Changing friends.
  • Having difficulties with family members.
  • Being secretive or dishonest.
  • Changing sleep habits, appetite, or other behaviors


As we age our bodies react differently to substances including cannabis.  Here are some of the health risks if you use cannabis:

Daily or near-daily cannabis use can:

  • Increase risk of psychosis and schizophrenia
  • Worsening anxiety and depression, and
  • Affects memory, concentration and ability to make decisions.

Regular use can lead to:

  • Sore throat
  • Hoarse voice
  • Coughing
  • Wheezing
  • Tightness in the chest
  • Chronic bronchitis

Smoking, vaping or eating cannabis products can lead to feelings of euphoria (happiness) and relaxation. It can also cause impairment, including:

  • Concentration and memory problems
  • Impaired motor skills and slower reaction time that can increase the risk of falls and injury.

Consuming too much cannabis or cannabis with high levels of THC can lead to over-intoxication. Symptoms can include:

  • Anxiety, panic and elevated heart rate
  • Nausea and vomiting
  • Paranoia and psychosis (i.e, hallucinations and delusions).

If someone you know has consumed too much cannabis and is not feeling well, go to the hospital or call 911.

Can I use cannabis if I’m taking medication?

You should talk to your healthcare provider if you’re considering using cannabis.

Cannabis can interact with your medications. Medications that can interact with cannabis include:

  • Pain medications
  • Heart medications and blood thinners
  • Sleeping pills
  • Ant-depressants and anti-anxiety medications
  • Heartburn medications
  • Anti-seizure medications
  • Drugs to treat HIV/Aids
  • ADHD medications

Cannabis concentrations have changed over the last few decades. In 1995, dried cannabis contained about 4% THC. Now it averages 15–20%. Some concentrates can contain more that 80% THC. Always read the label to check the amount and concentration of TCH and CBD.

You can learn more about Cannabis use for Older Adults in the Guide.

Know where to go for help.

If you are concerned about yourself or someone else, seek help from:

Signs you may need help with your cannabis or other drug use include:

  • Ignoring responsibilities at work, school, or home.
  • Giving up activities that you find important or enjoyable.
  • Using the drug more often.
  • Feeling unable to cut down or manage your use.
  • Changes in mood (e.g., feeling irritable and paranoid).
  • Changing friends.
  • Having difficulties with family members.
  • Being secretive or dishonest.
  • Changing sleep habits, appetite, or other behaviors