Cannabis and Health Effects

Health effects

Cannabis can be harmful to mental and physical health, especially if someone uses:

  • while under the age of 25
  • often, daily or near daily use
  • with other drugs, like tobacco or alcohol
  • high THC (delta-9-tetrahydrocannabinol) strains
  • while pregnant or breastfeeding
  • while operating a motor-vehicle
Short-term and long-term effects

When making a decision about using cannabis, it’s important to consider the short-term and long-term health effects. The effects of cannabis can be different for each person depending on genetics,  how much cannabis is used, how it is used and what type of cannabis.

Effects from smoking, vaping or dabbing cannabis can:

  • be felt within seconds to minutes
  • take up to 30 minutes to feel the full effects
  • last up to six hours or longer

Compared to smoking or vaping cannabis, effects from using edible cannabis may not be felt right away. Wait until the full effects are felt before consuming more. 

Effects from an edible cannabis product can:

  • be felt as quickly as 30 minutes to two hours
  • take up to four hours to feel the full effects
  • last up to 12 hours
  • some residual effects can last up to 24 hours

Some key health effects may include:

  • making it harder for you to learn, concentrate and remember things
  • affecting your mood and feelings (e.g. anxiety, fear or panic)
  • affecting mental health (e.g. triggers paranoia, delusions or hallucinations and psychotic episodes)
  • impairing your ability to drive safely or operate equipment as it reduces your ability to react quickly
  • risk for dependence and addiction

Learn more about what you need to know if you choose to consume cannabis

Canada’s Lower-Risk Cannabis Use Guidelines

There are risks of using cannabis for immediate and long-term health. The main risks include cognitive and memory issues, hallucinations and impaired perception, impaired driving, injury and death, mental health problems, a dependence on cannabis, breathing problems and problems with the development of a baby when used during pregnancy and breastfeeding.

  • The safest choice is no cannabis use at all.
  • Delay the use of cannabis until later in life. Using cannabis at an earlier age increases health and social issues.
  • Choose lower risk cannabis products with lower tetrahydrocannabinol (THC) levels.
  • Avoid synthetic (man made) cannabinoids as they have higher THC levels.
  • Avoid smoking cannabis and choose safer methods of using.
  • If you do smoke cannabis avoid deep inhaling and breath holding.
  • Reduce and limit the amount of cannabis you use.
  • Wait six hours after using cannabis before using any type of vehicle or machinery.
  • Do not use cannabis if you are pregnant, breastfeeding or you are at risk of mental health problems.

For more information, see Canada's Lower-Risk Cannabis Use Guidelines.

 Effects of combining cannabis with other substances

If you choose to consume cannabis in any form, avoid combining it with nicotine, alcohol, drugs, medications and other products as it may negatively affect your health. Some key known effects and risks associated with combining cannabis with other substances include:

Cannabis and alcohol

  • when cannabis is used with alcohol, it increases the strength of THC which can lead to adverse side effects
  • simultaneous use of alcohol and cannabis are associated with increased in intoxication and impairment
  • increases the risk of injury, falls or death

Learn more about the effects of cannabis and alcohol

Cannabis and tobacco 

  • cannabis can increase your rate of smoking tobacco
  • smoking tobacco can increase your rate of smoking cannabis
  • using both cannabis and tobacco simultaneously can result in greater risk for addiction and health risks like cancer, cardiovascular and respiratory disease

Learn more about the effects of cannabis and tobacco

Cannabis and medications

  • may alter the effect of prescription and non-prescription drugs
  • talk to your healthcare provider or pharmacists about ways to reduce your risks

Learn more about the effects of cannabis and medications

Cannabis use while pregnant and breastfeeding

Cannabis use in any form while pregnant and breastfeeding may have negative effects on both you and your baby. Do not use cannabis if you are trying to get pregnant, are pregnant, breastfeeding or parenting your child. If you have further questions, please contact your health care provider.

 Cannabis can affect you and your partner when you are trying to become pregnant by:
  • changing your menstrual cycle
  • lowering sperm count
  • reducing sperm quality

Cannabis crosses the placenta and your baby absorbs the chemicals that are in cannabis. Do not use cannabis while you are pregnant. If you are using cannabis for nausea, talk to your doctor about safe alternatives that are less risky to your baby’s growth and development.

Some immediate effects of cannabis use during pregnancy include:

  • low birth weight
  • pre-term birth
  • lower IQ scores
  • impulsivity and hyperactivity
  • brain development slows

Some effects of cannabis use during pregnancy that affect your child later in life include:

  • decreased ability to self soothe
  • sleep disturbances
  • poor memory
  • attention difficulties
  • hyperactivity and impulsivity
  • difficulty learning
  • depression and anxiety
  • reduced school performance
  • more likely to start using substances

Breastfeeding is the healthiest choice for your baby. Do not to use cannabis while you are breastfeeding. Cannabis passes into the breast milk and is taken into the baby’s fat cells and their brain.

Cannabis can affect your breastfed baby by:

  • slowing baby’s movements and responses
  • slowing baby’s brain development
  • baby becoming sedated

Cannabis can affect breastfeeding by:

  • lowering mother’s breast milk supply
  • baby having poor suck
  • baby becoming drowsy

Sources: Risks of Cannabis on Fertility, Pregnancy, Breastfeeding and Parenting and Women and Cannabis

Additional resources:

Related pages


Contact Us