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​​​​​​​​​​​​​​​​​​​​​​​​What is cannabis?

Cannabis (marijuana) is a drug that is made up of the leaves, flowers, and buds of the cannabis plant. People may use cannabis for medical or non-medical reasons.

THC and CBD are the two main cannabinoids in the cannabis plant that are studied, though there are more than 100. THC affects how you think, act, and feel. It can make you feel "high." CBD can help you feel relaxed without the "high".

There are many types, or strains, of cannabis. Each strain has a different THC-to-CBD ratio. Because of this, some strains have different effects than others. For example, if a strain of cannabis has a higher ratio of THC to CBD, it's more likely to affect your judgment, coordination, and decision making.​

How is it used?

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 100mg/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.

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.

What are the health effects of cannabis?

When you use cannabis, you may be putting your health at risk.

Short-term health effects.

People often use cannabis for the way it makes them feel. Using it may make them:

  • Feel relaxed or "high".
  • Have less chronic pain or nerve (neuropathic) pain.
  • Feel hungry so they may eat more.

But it may also cause unwanted side effects, such as:

  • Impaired short-term memory and ability to concentrate.
  • Poor judgment and 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 may feel the effects of cannabis depends on several things, including how it was taken. For example, when cannabis is smoked, the effects can usually be felt within seconds after inhaling. On the other hand, when cannabis is eaten, it can take several hours to feel the full effect. Since the effects aren't felt right away, people may think they need more and use too much. To avoid this, start with small amounts until you know how edibles affect you.

How much cannabis you've used and how long you've been taking it can also affect how your body responds to it. You may feel the effects of cannabis for hours after you use it.

Long-term health effects.

Long-term regular use of cannabis may lead to problems such as:

  • Trouble with learning, memory, and concentration. This is most likely if regular heavy use begins in the teen years.
  • Lung problems, if you smoke cannabis. This can lead to coughing or wheezing and lung infections like bronchitis.
  • Mental health problems like anxiety, depression, and psychosis. This is more likely if you have a personal or family history of these disorders or use cannabis products that have high levels of THC.
  • Cannabis use disorder. Some people who regularly use cannabis may find it hard to control their use and keep using cannabis even though it's having harmful effects on their lives.
    • Increased risk for Increased risk for nausea and vomiting (cannabinoid hyperemesis syndrome​, or CHS​). People who have CHS may feel very thirsty and have belly pain and diarrhea. They may vomit more than 20 times a day. Bouts ​of vomiting may last more than 24 hours.​

    Health effects of use during pregnancy and breastfeeding.

    Using cannabis is not safe for you or your baby. If used during pregnancy, it can harm a developing baby (fetus). It can pass through the placenta to your growing baby. THC can then build up in the baby's brain and fat cells, and can stay in their body for weeks.

    Cannabis can cause prob​lems for you during your pregnancy and when it is time for your baby to be born. It may also affect your baby both before and after he or she is born. These risks get higher, the more cannabis is consumed.

    Cannabis may cause:

    • Lower birth weight.
    • Problems with brain development, learning, and behaviour.
    • Problems with sleep and self-soothing (being able to calm themselves).
    • Slower growth.
    There is no known safe amount of cannabis (marijuana, hashish, hash oil) to use while breastfeeding. It can pass from the mother's breast milk to the baby during breastfeeding. If you use cannabis, it may:
    • Make you less able to supervise and care for your baby.
    • Make it harder to breastfeed.
    • Make it harder to tell when your baby is hungry.
    • Change your mood.
    • Change how you make decisions (your judgment).
    It's safer not to use cannabis when you're pregnant or breastfeeding.​

    Health effects of use in young people.

    Using cannabis before the age of 25 can affect a young person's brain development, as well as emotional and social development. Cannabis affects the parts of the brain that deal with judgement, decision making, and emotions. This can make it harder for young people to think, learn, reason, remember, solve problems, and make good choices. They may be less able to control their emotions and actions. For example; they may engage in risky b​ehaviours like driving when “high”, having unsafe sex, binge drinking, or using other drugs.

    Young people who use cannabis regularly may be more likely to have anxiety and depression than others wh​o don’t. They may have more problems in school, relationships, and work.

    Some young people who regularly use cannabis may develop cannabis use disorder. They may find it hard to control their use and keep using cannabis even though it's having harmful effects on their lives.

    Can regular use lead to cannabis use disorder?

    Some people who regularly use cannabis may develop cannabis use disorder. This can range from mild to severe (dependency). They may find it hard to control their use and keep using cannabis even though it's having harmful effects on their lives.

    The risk of cannabis use disorder is higher in people who:

    • Start using cannabis when they're young.
    • Use it every day.
    • Have other substance use disorders and mental health disorders.

    People who use cannabis often and then quit may have withdrawal symptoms. These include anxiety, trouble sleeping, and intense cravings for the drug.

    How can you reduce the risk of harm from cannabis use?

    Using cannabis isn't risk-free. But there are things you can do to reduce your risk of getting sick or injured.

    Lower-risk use.

    • All forms of cannabis use have health risks. The only way to completely avoid these risks is by choosing not to use cannabis.
    • You will lower your risk of cannabis-related health problems if you choose to start using cannabis later in life. The earlier in life you begin using cannabis, the higher your risk of serious health problems.
    • Choose products that have low levels of THC or a higher ratio of CBD to THC. Read the label of any products you're thinking about trying. The type or strain, strength, and effects of cannabis can vary greatly.
    • Don't use synthetic cannabis, such as K2 and Spice. These drugs are stronger than cannabis and can have very bad side effects. While cannabis is in the name, these synthetic drugs do not come from the cannabis plant.
    • Avoid smoking cannabis. The smoke can damage your lungs. Other forms of cannabis use, such as vaping or edibles, are better for your lungs but still have health risks.
    • If you choose to smoke cannabis, avoid breathing in deeply or holding your breath.
    • Try to limit your cannabis use to 1 day a week, at most.
    • Don't drive or operate machinery after using cannabis. Using cannabis may affect your judgment, coordination, and decision making. It can also increase your risk of being in a car crash. Make a plan to get home safely. For example, choose a designated driver or take a taxi or bus for a safe ride home.
    • Avoid cannabis if you have a personal or family history of psychosis or substance use problem. Pregnant women should not use cannabis at all.
    • Avoid combining any of the risky behaviors described above.

    ​Please visit Canada's Lower-Risk Cannabis Use Guidelines​ for the full list.

    Reaction with your medicines.

    • ​Cannabis can react with your medicines (called an interaction).
      • Cannabis can be dangerous if you use it with medicines that make you sleepy or control your mood. These include sedatives, anxiety drugs, antidepressants, and opioids.
      • Be aware that cannabis can cause changes to your blood pressure. This is especially important if you take medicine to control your blood pressure.
      • Cannabis can also increase the chance of bleeding if you're on blood thinners.
    • Talk to your healthcare provider before using cannabis.

    Know what you're using.

    • Understand how soon you may feel the effects of the product you use, and how long those effects may last. The product label may also have this information.

    Keep others safe.

    • Store cannabis in a safe and secure place. This is especially important with edible cannabis, which can be easily mistaken for treats or snacks. Make sure that children, friends, family, and pets can't get to them.
    • Protect others from second-hand smoke. It is unsafe to smoke or vape with children or others present. Second-hand cannabis smoke can cause babies and young children to be sick and it can affect their levels of alertness, understanding, and judgement. If you're around someone who is smoking cannabis, you may feel some effects of the drug.
    • It is impossible to minimize the risks of second-hand smoke without removing it entirely. To eliminate the risks with second-hand smoke, consider consuming oils and edibles.
    If you are concerned about your own, or someone else's use of cannabis, alcohol, or another drug, please contact Health Link at 811, 24 hours a day, 7 days a week or call Addiction Helpline 1-866-332-2322.

Current as of: April 9, 2019

Author: Adapted with permission of Healthwise ®