Because cannabis can pose many health risks, Health Canada has suggested that the following people should avoid using cannabis:


The human brain does not finish developing until the age of 25, making youth more vulnerable to the health impacts of cannabis than most adults are. Using cannabis in early teen years can change the structure of the brain as it develops. Daily or almost daily use also seems to have different effects on youth than it does on adults, such as lasting problems with attention span, memory and other mental functions.

Although the risk of becoming dependent on cannabis is relatively low (approximately nine per cent of users, or one in 11), it is much higher for people who use cannabis from a young age like early teens (approximately 17 per cent of youth users, or one in six people). Early use also increases the risk of experiencing psychotic symptoms or developing schizophrenia.

Pregnant or breastfeeding women

Using cannabis when pregnant could be harmful to both mom and baby. Heavy cannabis users, particularly those who mix it with tobacco, have a greater risk of having a premature baby. The baby may also experience lower birth weight, lower alertness and slower growth.

THC passes into breastmilk and then enters the baby’s brain and fat cells, where it can remain for weeks. Mothers’ cannabis use has been associated with a range of impacts on their baby, including sleep disturbance and poorer school performance later on. Because breastfeeding is still the healthiest choice for babies, it is recommended that women stop using cannabis while pregnant or breastfeeding.

For more information, please see: https://resources.beststart.org/product/a30e-risks-of-cannabis-booklet/

Men who want to be dads

Cannabis has been shown to reduce sperm count, sperm mobility, and sperm concentration. Cannabis may also increase abnormal sperm structure. These effects can make it more difficult for a couple to become pregnant.

People with a personal or family history of psychosis, schizophrenia, or bipolar disorder

Scientific studies have looked at the connection between cannabis use and psychosis. Psychosis is a serious mental disorder that impairs a person’s sense of reality with hallucinations or delusions. Those studies have found that using cannabis heavily, particularly if there is a history of mental illness in the family, may trigger a psychotic reaction, and regular use may increase the risk that some people will experience longer-lasting psychotic episodes. Evidence does not show that cannabis directly causes schizophrenia, however, people who use it at a young age or heavily (daily or almost daily over months or years) have a higher risk of developing the illness.

People with a personal or family history of depression

Cannabis may also worsen the symptoms of depression. If you struggle with depression, it is recommended that you speak with you health care provider about other ways of improving your mental health.

People with serious liver, kidney, heart or lung disease

Frequent cannabis use can negatively affect many different organs in your body. It is important that you talk to your health care provider before using cannabis if you have any of these diseases.

People taking other medications

Cannabis may interact with several drugs. If you are currently using or thinking of using cannabis, make sure to tell your health care provider and discuss which prescription drugs, non-prescription drugs, or herbal products you are currently taking.

This is especially true for any product that slows down the central nervous system, causing drowsiness. These may include sleeping pills, tranquilizers, some pain medications, some allergy or cold medications, or anti-seizure medications.

Other products that may interact with cannabis include: antiretroviral drugs used to treat HIV/AIDS, certain anti-depressants, stomach acid inhibitors, certain antibiotic and antifungal medications, certain heart medications, and Saint John’s Wort.1

1Health Canada. Consumer Information – Cannabis (Marijuana, marijuana).