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Legal doesn’t mean safe. No drug is without risk. The easiest way to avoid any potential harm from non-medicinal (“recreational”) cannabis is to simply avoid using it.

Anyone who does consume cannabis should follow Canada’s Lower-Risk Cannabis Use Guidelines, consider using lower strength THC concentration cannabis products, and consume less frequently. If you feel you may have a cannabis use disorder, consult your healthcare provider. It’s also important to consult your healthcare provider if you’re considering using cannabis for medical reasons.

The following represents a cautious health perspective regarding what is currently known about non-medicinal use of cannabis.

Mental health and cannabis use disorder

Cannabis can affect your mental health and increase your risk of severe problems like psychosis, schizophrenia and a cannabis use disorder. People with a personal or family history of mental health concerns are at greater risk of cannabis-related mental health problems. Adolescents and young adults (under age 25) with a personal or family history of mental health problems are at an even greater risk. Frequent or regular cannabis use can lead to ca cannabis use disorder or dependency.  Seek support if you or someone you know is having issues with cannabis use.

Driving under the influence of cannabis

Cannabis use reduces your ability to drive safely with negative impacts on reaction time, coordination, attention and decision-making. These effects can start within minutes after inhaling cannabis and last for up to 12 hours if you consumed an edible. However, many other factors impact how cannabis can affect you. In general, it’s best to avoid driving after using cannabis.

Adolescents and young adults (<25)

It is best to avoid cannabis use until age 25 or older. Critical brain development occurs until the mid-twenties and cannabis use can affect this development. Earlier and frequent use of cannabis increases your risk, but even occasional use can cause problems. These problems include difficulties with memory, thinking, attention span, mental health problems and cannabis use disorder. For those who choose to consume cannabis before the age of 25, delaying use until a later age is recommended.

Harm Reduction

Anyone who consumes cannabis should follow Canada’s Lower-Risk Cannabis Use Guidelines and consult their healthcare provider. To reduce the risk of harm, cannabis should be avoided until age 25 or older.


Edible cannabis can take 30 minutes to 2 hours to take effect. Because of this delayed effect, there’s a risk of overconsumption or poisoning. To reduce your risk, begin with a small amount and wait one hour before deciding whether to take more.

Unintentional consumption (children and pets)

Keep cannabis products in their original packaging from a licensed retailer.  If unable to do so, store cannabis products in child-resistant packaging which clearly identifies cannabis contents, in a locked area out of sight and reach. Children can easily accidentally eat cannabis products especially if they’re in an edible form (for example, brownies or baked goods). Following legalization of cannabis in Colorado, the number of children who needed to be seen in an emergency department after accidentally eating cannabis almost doubled. Cannabis products, especially edibles, creams, oils, vape cartridges can be difficult to discern from non-cannabis products.

Physical health

Cannabis is not harmless. Individual responses to the drug differ. Effects can include: increased appetite, increased heart rate, decreased blood pressure, decreased ability to maintain balance and stability, poor memory, difficulty thinking, distorted perceptions (sights, sounds, time, touch), drowsiness or restlessness, anxiety, red eyes, dry mouth and throat and irritated respiratory system (from smoking).

Prenatal health

Cannabis should not be used during pregnancy and is not recommended to treat morning sickness. Cannabis use during pregnancy exposes the baby to cannabis and other chemicals from the mother’s blood. Smoking cannabis also reduces the amount of oxygen supplied to the fetus, which can lead to babies with lower birth weight. Cannabis use during pregnancy has also been associated with developmental effects in children and adolescents, including decreases in memory, ability to pay attention, reasoning and problem-solving skills, hyperactive behaviour and increased risk for future substance use.

Protection from second-hand cannabis smoke/vapour

Avoid smoking or vapourizing cannabis indoors or around children. Cannabis smoke and vapour can expose children to THC and toxins. This smoke could harm the lungs of infants and children and affect their alertness, understanding and judgment.


Cannabis should be avoided if breastfeeding. THC from cannabis passes into breast milk and to the baby’s fat cells and could affect the baby’s development. Breastfeeding parents should consult their healthcare provider regarding the benefits of breastfeeding versus the potential risks of exposure to cannabis on infant development.

Preconception health

Men and women thinking of becoming pregnant should avoid cannabis. Cannabis use may affect the ability to become pregnant. Heavy cannabis use has been linked to changes in menstrual cycles in women, and lower sperm quality in men. Some studies have shown that the use of cannabis during pregnancy, and while breastfeeding, may be associated with increased risk for low birth weight, preterm labour, short- and long-term learning, development, and behavioural issues.

Parents and caregivers

Avoid using cannabis while parenting or caring for others. Cannabis use may affect how parents interact with their children, and lowers their ability to make good decisions and attend to their children’s needs. The effects of cannabis can last for several hours. If you plan on using, ensure to always have a sober caregiver for your baby, child or other dependent.

Personal cultivation (growing cannabis)

In Ontario, personal cultivation is limited to 4 plants per household. Cultivating cannabis can have risks. Opting for the Ontario Cannabis Store online or legitimate retailers in person offers a safe method for consumers to access a carefully controlled product. Federally licensed producers offer a safe method for Ontarians to access cannabis for medical purposes.

If growing cannabis, follow your condominium rules or lease agreement. Make sure children and animals do not have contact with or access to growing plants (fenced area outdoors; locked room indoors). Control child and pet exposure to the areas of the home where plant parts are processed (often the kitchen), and where waste materials have been discarded.

If growing indoors, biological hazards (like mould) can occur. Mature cannabis plants increase indoor humidity 5-7 times more than regular house plants. Chemical and lighting hazards also pose health and safety risks.

  • Maintain relative humidity below 65% in indoor growing spaces.
  • Dispose of mouldy plants immediately, and in a way that does not allow unsuitable material to be reprocessed.
  • Vacuum rather than sweep.
  • Use small-scale air cleaners/ventilation.
  • Install CO monitors with audible alarms. Do not use space heaters or generators indoors.
  • Choose pesticides that are non-persistent and have low volatility. Wear proper personal protective equipment when applying pesticides.
  • Always operate lamps with a compatible ballast, rated fixture (open/closed, wattage), and socket. 
  • Choose LED lighting systems to reduce energy usage and heat output.

Cannabis and Alcohol

The co-use of cannabis and alcohol should be avoided.  Simultaneous use of cannabis is associated with more harmful consequences than the use of either substance alone. Co-use has been found to increase the likelihood of social and behavioural substance-related consequences such as legal, health, relationship and academic problems.

Extracts, concentrates or products containing high amounts of THC

Using products containing high amounts of THC is associated with a higher risk of harms such as altered cognitive functioning, psychosis or psychiatric disorders, dependence, tolerance and withdrawal.  Individuals who are new to cannabis should avoid high-strength cannabis products.

Therapeutic use

Anyone who is considering the use of cannabis for medical purposes should consult with a healthcare provider as evidence on cannabis for medical purposes continues to emerge.

Older Adults

Older adults are more vulnerable to the effects of cannabis due to physiology, psychological, social and pharmacological circumstances.  Older adults should consult with a health care provider before initiating use.


Everyone has a role to play in workplace health and safety.  Workers performing work when they are impaired or unfit may introduce hazards to the workplace, to themselves or to others. Accommodations may be required to reduce any risks.

Oral Health

Smoking cannabis can cause periodontal diseases, life threatening oral cancers and caries.