Information about cannabis

Information about cannabis

Last updated: September 17, 2024

Learn how cannabis makes you feel and about related health risks and safety considerations.

You can also find more information and resources on cannabis in our Cannabis Health Feature and the following topics on our website.

For information from the Government of British Columbia on cannabis legislation, regulations, impacts on travel, growing at home and more, please visit Get Cannabis Clarity.

On this page:

Considerations for using cannabis

It is important to take particular caution if you are young or have certain conditions. To learn more about reducing risk if you use cannabis, please visit Lower Risk Cannabis Use Guidelines, Canadian Research Initiative in Substance Misuse.

You are more likely to experience harm from regular or frequent use of cannabis if you are under the age of 25. Your brain is still developing at this age. The earlier you start using cannabis, or the more heavily you use it, the more harm it can do. For more information please visit:

Certain conditions increase the risk of harm from using cannabis. Avoid cannabis use if:

  • You have a history of psychotic disorders, unless you are under careful psychiatric monitoring
  • You have a history of low blood flow to vessels that supply the heart, known as “cardiac ischemia” or “cardiac artery disease”. Those receiving digitalis or other cardiac medications should only use cannabis under careful supervision by a medical doctor
  • You are suffering from an infectious disease
  • You are pregnant or breastfeeding. You could transfer harmful substances in cannabis to your developing baby while pregnant or through your breast milk

Health effects of cannabis use during pregnancy and breastfeeding

Cannabis use during pregnancy can affect a developing baby (fetus). The chemicals in cannabis can cross the placenta. Cannabis use during pregnancy is associated with low birth weight. The chemicals can also pass from the mother's breast milk to the baby during breastfeeding and cause problems for the baby. These problems may include drowsiness and poor suckling. It may be harder for your baby to get enough breastmilk. Exposure to cannabis during pregnancy and breastfeeding may affect a child’s brain development, learning and behaviour.

For more information please visit Health effects during pregnancy and breastfeeding: Government of Canada.

Using cannabis safely

Every form of cannabis poses a risk to your health. The only way to completely avoid the risks is by choosing not to use cannabis. If you’re going to use cannabis, here are tips safer cannabis use:

  • Choose lower strength products. For example, lower THC (delta-9-tetrahydrocannabinol) content or a higher ratio of CBD (cannabidiol) to THC
  • When smoking cannabis avoid deep inhalation or breath-holding
  • Smoking cannabis is the most harmful. Consider non-smoking options
  • Don’t use synthetic cannabis products
  • Avoid frequent use
  • Avoid combining cannabis with alcohol and/or other drugs and substances
  • Only use cannabis and cannabis products that come from legal sources

For more information, please visit:

Intoxication from second-hand cannabis smoke

If you're around someone who is smoking cannabis, you may feel some effects of the drug. People who are allergic to cannabis may be more sensitive to second-hand cannabis smoke. To protect others from second-hand smoke, smoke cannabis outside or choose a room where you can open a window or use a fan to get the smoke outside. For more information, please visit:

Short and long-term effects of cannabis use

To learn more about the short- and long-term effects, please visit Health effects of cannabis, Government of Canada.

Addictiveness of cannabis

Cannabis use can lead to dependency. Avoid cannabis if you have a predisposition to or family history of psychosis, addiction, substance use disorder or problems with substance use. Close to 1 in 3 people who use cannabis will develop a problem with using it. Close to 1 in 10 people who use cannabis will develop dependency. This statistic rises to about 1 in 6 for people who started using cannabis as a teenager.

People who use cannabis regularly can develop psychological and/or mild physical dependence. People with psychological dependence may be preoccupied with using cannabis.

For more information, please visit Is Cannabis addictive?, Government of Canada.

Dangers of cannabis use

Using cannabis regularly (daily or almost daily) and over a long time (several months or years) can hurt the lungs if smoked and make it harder to breathe. Cannabis smoke contains many of the same harmful substances as tobacco smoke.

Cannabis can also affect mental health. Your mental health is more likely to be affected if you use cannabis regularly and frequently over time. You are more likely to experience anxiety, depression, psychosis, and schizophrenia. Cannabis products with a higher THC concentration can make the mental health effects of cannabis use worse. Examples of cannabis products with higher THC concentration include “shatter”, wax and dabs. This can happen with occasional or even one-time use for some individuals. Stopping or reducing cannabis use can improve outcomes

There is also a chance cannabis use can make you physically dependent or addicted. About 9% of people who use cannabis in their lifetime will become dependent on cannabis. This rate increases to 16% for people who start using cannabis as a teenager. Up to 1 out of 2 people who use cannabis daily will become dependent.

Combining cannabis with alcohol and driving is dangerous and can result in accidents.

For more information please visit the Cannabis: CAMH webpage.

Getting behind the wheel while impaired by drugs is not only dangerous, it’s against the law.

The legal limit is 2ng of THC per mL of blood. It is a more serious offence to have more than 5ng of THC per mL of blood. Police may administer a saliva test to determine if THC is present in your system. If so, the police can then ask you to provide a blood test.

THC impairment can last for more than 24 hours after cannabis use, well after other effects may have faded. There is no standard waiting time to drive after using cannabis. If you are using cannabis, do not drive. Instead, stay over, call a taxi, share a ride, use public transit or have a designated driver.

The time it takes for the psychoactive effects of THC in cannabis to wear off depends on:

  • How much and how often you have consumed THC
  • Whether you smoked, vaped or ate it
  • Your age, mood or if you have pre-existing medical or psychiatric conditions
  • Whether you’ve taken any alcohol or other drugs

For more information please visit:

The need for medicinal cannabis despite legalization of recreational use

British Columbians over the age of 19 years can buy cannabis from licensed private and public cannabis retail stores or the BC Cannabis Stores website. Some authorized individuals may still wish to get medical cannabis through the federal system.

If you are planning to use cannabis for a medical purpose, talk to your health care provider. Discuss the pros and cons of using cannabis to treat your medical condition. Ask about possible interactions between cannabis and other treatments you are taking.

The new federal regulations have improvements for authorized individuals who get cannabis for medical purposes directly from federally licensed producers/sellers. These improvements include:

  • The ability to request the return of their medical document from a federally licensed seller
  • The ability to request the transfer of their medical document to a different federally licensed seller
  • The effective date on the registration document will be the issue date instead of the day the health care provider signed it
  • Removal of the 30-day limitation period for buying cannabis from a federally licensed seller (to ensure no break in a patient's supply)
  • A broader range of permitted products
  • Access to an increasing number of licensed producers and sellers. Health Canada has licensed more producers in the last year than in the 4 previous years combined
  • The increasing number of licensed producers/sellers makes prices more competitive
  • More licensed producers/sellers, increases supply of quality-controlled cannabis and increases availability of a range of products
  • The rules are different if you use medical cannabis. Landlords and employers are required by law to accommodate medical cannabis users the same as they would anyone else with a disability or medical condition
  • You’re allowed more cannabis in your possession. You can have whichever is less of 150 grams or a 30-day supply of dried cannabis (or the same amount in cannabis product). This is in addition to the 30 grams allowed for non-medical purposes

More reasons to use the federal system to access cannabis for medical purposes include:

  • The federal system is the only way for patients under the age of 19 years to access cannabis for medical purposes
  • Cannabis purchased via this system may be claimed as a medical expense on tax returns
  • Some federally licensed cannabis sellers offer a reduced price on compassionate grounds for people purchasing medical cannabis
  • If you grow your own medical cannabis, you may be able to grow more plants by registering with the federal program
  • Cannabis cultivation or smoking/vaping may not be allowed at your place of residence. Exceptions to these rules are more likely for those with a medical authorization

For information on renting while using medical cannabis call the Office of Medical Cannabis at 1-866-337-7705. Also see Cannabis for medical purposes under the Cannabis Act: information and improvements, Government of Canada.

Difference between medical and non-medical cannabis

Patients taking cannabis for medical reasons generally use cannabinoids to alleviate symptoms. Usually, patients try to minimize intoxication. Non-medical users may be taking cannabis for euphoric effects. Some people use cannabis for both purposes.

Many patients access medical cannabis through the federal system under the federal Cannabis Act. Under the federal system, a health care provider authorizes medical cannabis use. The health care provider provides a medical document authorizing individuals to:

  • Get cannabis from a federally licensed producer/seller
  • Apply to Health Canada to grow their own cannabis
  • Designate someone else to grow cannabis for them

Non-medical cannabis can be legally purchased for medical or non-medical use through at private licensed cannabis retail stores, public government run retail stores and online from the BC Cannabis Stores. For more information please visit Medical Cannabis.

Duration of cannabis effects

Impairment can last for more than 24 hours after cannabis use, well after other effects may have faded.

You can feel the effects within seconds to minutes of smoking, vaporizing or dabbing cannabis. These effects can peak within 30 minutes and last up to 6 hours with some residual effects lasting up to 24 hours. If you eat or drink cannabis, these effects can peak within 30 minutes to 2 hours and can last up to 12 hours with some residual effects lasting as long as 24 hours.

When eating or drinking cannabis, it can take up to:

  • 2 hours for you to start to feel the effects
  • 4 hours for you to feel the full effects
  • 12 hours for acute effects to subside

Be extra cautious if you are not used to eating or drinking cannabis products that contain THC. Start with a low dose (such as 2.5mg THC) and wait until you feel the effect before deciding if you want to take more. This could mean waiting 2 hours or more before increasing the dose. Call 9-1-1 or poison control (24-hour Line: 604-682-5050 or 1-800-567-8911) if you or someone else is experiencing unpleasant effects from too much cannabis.

For more information on when effects may start, peak and how long they last, please visit:

Effects of cannabis on mood and perception

Cannabis affects mood and perception in both positive ways and negative ways. Some of the preferred and anticipated effects include:

  • Relaxed or intoxicated ("high")
  • Less chronic pain or nerve (neuropathic) pain
  • Hungry so you eat more
  • Less nauseous. Or you may have less vomiting due to cancer chemotherapy drugs

However, cannabis can also cause unwanted side effects, such as:

  • Impaired short-term memory and ability to concentrate
  • Poor judgment and coordination
  • Anxiety or paranoid thoughts
  • Psychosis, which is disordered thinking. Psychosis can include losing touch with reality and/or experiencing delusions (false beliefs). It may cause hallucinations such as hearing voices or seeing things that are not there
  • Faster heart rate
  • Red eyes and dry mouth
  • Dizziness
  • Drowsiness
  • Nausea and vomiting
  • Changes in blood pressure

For more information please visit Cannabis and Your Health.