​​​​​​​​​​​​​​​​​​​​​​​Cannabis is a drug made up of the leaves, flowers, and buds of the cannabis plant. Cannabis may be used for medical and non-medical reasons.

There are more than 100 different chemical compounds, or cannabinoids, in the cannabis plant. Tetrahydrocannabinol (THC) and cannabidiol (CBD) are the 2 most known and most often studied.

• THC changes how you think, act, and feel and can make you feel "high".
• CBD can make you feel relaxed without the "high".

There are many types (strains) of cannabis. Each strain has a different amount of THC and CBD so the effects are different for each. For example, if a strain of cannabis has more THC than CBD, it's more likely to change how you:

• think, act, and feel
• move your body (your coordination)
• make decisions (your judgment)

​​​​​​​​​​​​​​​​​There are several ways to use cannabis. You can smoke, vapourize, eat, drink, swallow, or absorb it through your body tissues.

Smoking or vaping

You can smoke cannabis as a dried plant or inhale it as a vapour (sometimes called vaping). If you choose to smoke or vapourize cannabis, start with 1 or 2 puffs. You should feel the full effects of the cannabis within 30 minutes.

When smoking or vaping cannabis, choose products with 100 mg/g (10%) or less THC. This will lower your risk of having an unwanted reaction (called an adverse effect). Look for the amount of THC on the label of the container.

It’s important to know that inhaling any type of smoke can be harmful. Even though vaping may be less harmful than smoking, there are still health risks and harms from contact with the chemicals in vaping products.

Eating, drinking, or swallowing

You can eat cannabis in foods or drink it as a brewed tea or in other beverages. These products are sometimes called edibles. You can also swallow cannabis as an oil or in capsules, or spray it in your mouth or under your tongue. These cannabis products are sometimes called extracts.

When eating, drinking,​ or swallowing cannabis, choose products that have 2.5 mg of THC or less, especially if you are a new user or only use cannabis once in a while. Look for the amount of THC on the label of the container.

It is important to know that:

• It can take up to 4 hours to feel the full effects after you eat, drink, or swallow cannabis.
• If you use more than the suggested dose during this time, you’re more likely to have an unwanted reaction.
• The effects of eating, drinking, or swallowing cannabis can be stronger and last longer than smoking or vaping. In some cases, the effects can last up to 12 hours.

Absorbing

Cannabis products that are put directly on your body, such as your skin, hair, and nails, are called topicals. Topicals may be a cream, lotion, oil, or come in other forms.

In general, these products don’t make you feel “high”. At this time, there isn’t much research on topical cannabis products.

Medical cannabis

Medical cannabis is cannabis used for medical reasons. Medical use of cannabis has been legal in Canada since 2001. To use cannabis for medical reasons, you must:

• have a document from your doctor that gives you permission to use it (Go to Health Canada to learn more.)
• buy your cannabis from a company that has a licence to sell it in Canada for medical reasons (called a licensed producer) or have approval from Health Canada to grow your own cannabis plants

If you use medical cannabis, it’s important that you only use your own supply. Do not share your cannabis with others or use someone else’s cannabis. Your doctor has given you permission to use medical cannabis for your condition. If you use someone else’s cannabis, it could cause unwanted effects.

What is medical cannabis used for?

Medical cannabis is sometimes used to:

• manage nausea and pain
• increase appetite
• relax muscles
• help you sleep
• prevent seizures, muscle spasms, and anxiety
• lessen inflammation

Even though medical cannabis may be used for many health conditions, research shows it may only help manage a small number of health conditions.

Are there medicines with tetrahydrocannabinol (THC) and cannabidiol (CBD)?

Your doctor may also prescribe medicines with THC and CBD that you get from a pharmacy. You don’t need the same type of permission from your doctor to use these medicines as you do for medical cannabis.

• Sativex is a medicine that can relieve pain and muscle stiffness. It has both THC and CBD. It is sometimes given to people with advanced cancer or multiple sclerosis. This drug is made with natural THC.
• Nabilone (Cesamet) is a medicine that helps manage nausea and vomiting in people taking chemotherapy to treat cancer. It may also improve appetite in people who have AIDS. Nabilone has synthetic THC.
  

Learn more about THC and CBD​.

More information about medical cannabis

If you’re thinking about using cannabis for medical reasons, talk to your doctor. You can also visit the Health Canada medical use of cannabis​ website for more information.

Non-medical cannabis

Non-medical cannabis is the legal, non-prescribed use of cannabis by people over the age of possession (in Alberta, this is 18 or older). Non-medical cannabis has been legal in Canada since October 2018. In Alberta, you can buy non-medical cannabis from a licensed store or online from a legal source.

​​​​​​​​​​​​​​​​​Some effects of cannabis happen right away, as soon as it’s used. Other effects can develop over time, the longer it’s used. These are called short- and long-term effects.

It’s important to remember that cannabis affects everyone differently. How you’re affected can change from one time to the next.

Short-term effects

Short-term effects of cannabis include:

• feeling relaxed or "high"
  
• feeling hungry
• trouble concentrating or remembering things that just happened (short-term memory issues)
• changes in judgment 
• less coordination
• anxiety or paranoid thoughts
• faster heart rate
• red eyes and dry mouth
• dizziness
• drowsiness
• nausea and vomiting
• changes in blood pressure

How soon and how long you feel the effects of cannabis depends on several things, including:

• how you used it (like smoking it, vaping it, or eating it)
• whether you have used alcohol or other drugs at the same time (this makes it more likely that you will have unwanted effects)
• whether you have used cannabis before

Using too much cannabis (called cannabis poisoning) can cause harmful effects. Signs of using too much cannabis include:

• changes in heart rate
• severe (extreme) nausea and vomiting
• anxiety, extreme confusion, panic attacks, or paranoia
• seizures

If you’re worried that you or someone you’re with has used too much cannabis, call:

• the Poison & Drug Information Service (PADIS) toll-free at 1-800-332-1414
• Health Link at 811
  
• 911 (in an emergency)

Long-term effects

Long-term, regular use of cannabis may lead to the following problems.

Learning, memory, and concentration problems
This is more likely to happen if you began using cannabis regularly and heavily in your teen years.

Lung problems
Smoking cannabis can cause lung problems that lead to coughing, wheezing, and lung infections like bronchitis.​

Fertility problems
Cannabis use may make it harder for you to have a baby. Using cannabis can cause menstrual cycle changes and increases the risk of testicular cancer, which can lead to low sperm count and quality.

Mental health problems
Cannabis use can make the symptoms of anxiety, depression, and bipolar worse. It can also increase your risk for thoughts of suicide and suicide attempts. Using cannabis can also increase your risk for psychosis (seeing or hearing things that are not real) and developing schizophrenia. This is more likely to happen if you have a personal or family history of these disorders or often use cannabis products with high levels of tetrahydrocannabinol (THC).

Cannabis use disorder
This condition can happen to people who regularly use cannabis. They may find it hard to control their use and keep using cannabis even though there are harmful effects.

You have a higher risk of cannabis use disorder if you:

• start using cannabis in your early teens
• use it every day or almost every day​
• use products with high levels of THC
• have other substance use disorders or mental health disorders

When you have cannabis use disorder, you may have withdrawal symptoms if you quit using cannabis.

Withdrawal symptoms may include anxiety, trouble sleeping, and having cravings or a strong desire for the drug.

Cannabinoid hyperemesis syndrome (CHS)
This is a condition that causes severe nausea and vomiting. Vomiting may happen more than 20 times a day and last more than 24 hours. You may also feel very thirsty, have belly pain, or diarrhea.​

Learn more about CHS, how to care for yourself, and when to get help.

If you’re worried about your own or someone else's use of cannabis, alco​hol, or another drug, call Health Link at 811 or the Addiction Helpline at 1-866-332-2322.

​​​​​​​​​​​​​​​​​​​​​When you use cannabis under the age of 25, it can change how your brain develops. This can have an effect on how you develop emotionally and socially. Cannabis affects the parts of the brain that control judgment, decision making, and emotions.

Delaying cannabis use until you’re over 25 years old can lower your risk of harmful health effects.

​If you are under 25 and use cannabis regularly, you may:

• have problems thinking, learning, reasoning, remembering, solving problems, and making decisions
• be more likely to have anxiety and depression than those who don’t use cannabis
• have more problems in school, relationships, and work

Using cannabis could also get in the way of your future goals. Young people who use cannabis regularly are less likely to finish high school or get a college degree.

Find out more about the effects of cannabis.

​​​​​​​​​​​​​​​​​​​As we get older, the effects of cannabis and other drugs that act on the central nervous system (brain and spinal cord) may be stronger. This can put you at higher risk for unwanted side effects.​

There is very little research on the effects of cannabis use on older adults. But it’s important to know that if you’re an older adult who uses cannabis, you may:

• cough more and have more phlegm (if you smoke it)
• make chronic obstructive pulmonary disease (COPD) symptoms worse (if you have COPD)
• have a higher risk of falling after using cannabis because it makes you feel impaired, tired, dizzy, or anxious
• have a higher risk of harmful substance use if you often spend time alone, don’t have support from others, have depression or anxiety or have recently lost a loved one
• have a higher risk of a drug interaction if you take more than one medicine to treat different medical conditions

If you’re thinking about using cannabis, ask your doctor or pharmacist to go over all your medicines with you before you use it. Find out more about the effects of cannabis and why it’s important to know how cannabis interacts with your medicines​.

​​​​​​​​​​​​​​​​​​​​​​​There are risks to using cannabis. But there are ways to lower your risk of harm.

Know the health effects

All forms of cannabis use have health risks​. The only way to completely avoid these risks is by choosing not to use cannabis.

Avoid using cannabis if you have a personal or family history of mental health problems or substance use problems.

If you choose to use cannabis:

• delay use until you are 25 or older
  • The earlier in life you begin using cannabis, the higher your risk of serious health problems.
• avoid smoking it, as the smoke can damage your lungs
  • Other forms of cannabis use, such as vaping or edibles, are less harmful for your lungs but still have health risks.
  • Avoid breathing in deeply or holding your breath as this may cause lung damage.
• limit your use as much as possible, such as 1 day a week or only on weekends
  • Using cannabis often is linked to a higher risk of health problems.
• ​avoid combining cannabis with alcohol, tobacco, or other drugs as this makes it more likely you will have unwanted effects.

Cannabis can react with your medicines (called an interaction) and affect your health. Medicines that interact with cannabis include:

• Pain medicines
• Heart medicines and blood thinners
• Sleeping pills
• Anti-depressants and anti-anxiety medicines
• Antibiotic and antifungal medicines
• Allergy, cold, and flu medicines
• Heartburn medicines
• Anti-seizure medicines
• Drugs to treat HIV/AIDS

​Before you try cannabis, talk to your healthcare provider about any medicines you use and how they might interact with cannabis.

Don’t use cannabis and drive

Don't drive or operate machinery after using cannabis. Also, don’t ride in a vehicle with someone who has recently used cannabis.

If you use cannabis while driving, you may:

• be less able to use your judgment or make decisions
• have less coordination
• have a higher risk of being in a car accident (collision)

If you use cannabis, make a plan to get home safely. Have a designated driver or take a taxi or bus.

Know what you’re using

It’s important to know what type of cannabis you’re using and what’s in it. Understand how soon you may feel the effects of the product you use, and how long those effects may last. Check the product label for this information.

• Choose products that have low levels of tetrahydrocannabinol (THC) or a higher amount of cannabidiol (CBD). Learn more about THC and CBD.
  • Always read the label of any products you're thinking about trying.
  • There are many different types and strengths of cannabis that can have different effects.
• Don't use synthetic cannabis products, such as K2 and Spice.
  • These drugs are stronger than cannabis and can have dangerous side effects. These include seizures, irregular heartbeat, hallucinations, and in rare cases, death.
  • These synthetic drugs don't have any cannabis in them.
• Always buy cannabis from a legal source. Learn more about legal cannabis in Alberta.

Keep others safe

If you use cannabis, it’s important to protect others from harmful effects.

• Don’t use cannabis when you’re around children.
  • Cannabis can make it harder for you to make decisions, respond to your children’s needs, or react in an emergency.
• Store cannabis in a safe and secure place (such as a locked box).
  • This is especially important for edible cannabis, which can be easily mistaken for regular food or drinks.
  • Make sure that children and pets can't get to them.
• Protect others from second-hand smoke or vapour.
  • It’s unsafe to smoke or vape with children or others around.
  • Second-hand cannabis smoke can cause babies and young children to get sick. It can make them less alert and affect their understanding and judgment.
  • If you're around someone smoking cannabis in a closed space with poor air flow, you may feel some effects of the drug.
  • Think about using oils and edibles instead of smoking or vaping cannabis.
  • Learn more about ​smoking and vaping exposures (second-hand and third-hand smoke and aerosol)
    

If a child comes into contact with cannabis, call:

• the Poison and Drug Information Service (PADIS) toll free at 1-800-332-1414
• Health Link at 811​
  
• 911 (in an emergency)

More information

Visit 10 ways to reduce risks to your health when using cannabis (PDF)​ for more information about lowering your risk of harm from cannabis.