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Alcohol & Other Drugs

Learn About Cannabis (marijuana)


Author: Canadian Institute for Substance Use Research


What is cannabis?

Cannabis is the scientific name for the hemp plant. Its leaves and flowers—often called marijuana—contain a psychoactive (mind altering) resin that can affect how we feel, think and act. It comes in various forms, including dried leaves and flowers or 'buds' (marijuana), pressed resin from flowers and leaves (hashish or hash), and concentrated resin extracted with a solvent (hash oil).

While often smoked in a joint or through a pipe or bong (water pipe), cannabis can also be vaporized into a mist. Some people bake or make tea with it, while others turn it into a tincture, a concentrated liquid absorbed by placing a drop under the tongue.


Why do we use cannabis?

Humans have been using cannabis for a range of reasons since ancient times. Some people have used it when socializing to help them relax and connect with friends. Others have used it for spiritual reasons or simply to experience an altered form of consciousness. And still others have used it to soothe anxiety, or manage medical conditions. Cannabis has many benefits but, like any drug, there are risks to using it.

Smoking a joint with a friend on a Friday night is one way to relax at the end of a busy work week. But sitting around for hours smoking joint after joint can create a dull atmosphere and make conversation meaningless. It can also increase the risk of making bad decisions, such as driving before the effects have completely worn off. And while cannabis may help to relieve stress or anxiety, continuing to use it as a coping strategy may harm our health and relationships.


What happens when we use cannabis?

When cannabis is inhaled, chemicals called cannabinoids are absorbed through the lungs and into the bloodstream, producing almost immediate effects. When swallowed, cannabinoids are absorbed through the stomach and intestine. This process takes longer, making it more difficult for the user to carefully manage the dose.

The effects of cannabis can be very different for different people. One person may feel relaxed, another full of energy, and another anxious. Sometimes the same person will have a different experience on a different occasion. A lot depends on the type and amount of cannabis we use at a given time. But other factors that affect us include our

  • past experiences with cannabis,

  • present mood and surroundings, and

  • mental and physical health condition.


There are more than 60 types of cannabinoids, but best known for its psychoactive properties is delta-9-tetrahydrocannabinol or THC.

Health effects

Cannabis can be both beneficial and harmful to our health. For instance, research shows cannabis can help relieve the symptoms of some medical conditions such as pain, nausea and muscle spasms. But heavy use is associated with a variety of harms including experiencing psychotic symptoms.

Many people who use cannabis socially say it helps them relax and increases their sense of well-being. But some people may feel anxious after using cannabis, affecting their interactions with others. And for a few hours after smoking a joint, a person may have a hard time remembering things, which may have an impact on friendships.

Over time, smoking a lot of cannabis can irritate the respiratory tract, increasing risk of chronic coughing, shortness of breath and wheezing. Like tobacco smoke, cannabis smoke contains cancer-causing toxins, though the risk of developing some cancers is less for cannabis users, partly because they tend to smoke less than tobacco users.

In the second three months of 2018, of Canadians aged 15 and older

17% of British Columbians consumed cannabis

14% of cannabis users with a valid driver's license drove within 2 hours of using

5% were a passenger in a vehicle driven by someone who consumed cannabis within two hours of driving



When is using cannabis a problem?

Using cannabis is a problem when it negatively affects our life or the lives of others. We may think this refers to people who regularly use large amounts of cannabis, but even using on a single occasion can sometimes lead to a problem. For instance, we may make a poor decision such as driving before the effects have worn off. What's important to recognize is the potential for adverse consequences as well as benefits related to the context of use and over time.

Cannabis use, especially regular use, by young people has particular risks. Like other psychoactive drugs, cannabis can interfere with normal brain development. Early use can also interfere with developing normal patterns of social interaction with peers and have a negative impact on well-being.

The reasons people use cannabis influence their risk of developing problems. For instance, if a person uses cannabis to have fun, only occasional social use may follow. But when a person uses cannabis to cope with a long-term problem such as chronic stress, then more long lasting and intense use may follow.

While most people who use cannabis do not become dependent on the drug, those who use cannabis frequently over a period of time may be putting themselves at some risk. A person who uses frequently may feel they need to use cannabis to feel normal and function during the day.

People who stop using cannabis after regular use may experience mild feelings of withdrawal, including irritability, loss of appetite and difficulty sleeping.

Mixing cannabis with other substances

It's not uncommon for people to mix cannabis with other substances to experience different feelings or offset unwanted side effects. But there are risks to combining cannabis with other substances, including intensified effects that may last longer than expected or wanted. The following are some common combinations and their related effects.

Alcohol and other depressants. These are substances that slow down our heart rate and make us feel more relaxed. Depressants affect coordination and other skills needed for safe driving. Cannabis in combination with even small doses of alcohol impairs our driving ability more than either drug used alone.

Stimulants. These are substances such as energy drinks or cocaine that increase our heart rate and make us feel more energetic. Combining cannabis with stimulants may cloud our judgement about how intoxicated we may be, potentially leading to risky behaviours.

Tobacco. Tobacco smoke contains many cancer-causing toxins. It is therefore safer to smoke cannabis by itself.


How to make healthier choices about cannabis

Whenever we choose to use cannabis, it is helpful to know what steps we can take to ensure that our use is the least harmful possible. The following are some useful guidelines to follow.

Not too much. Managing how much we use in a given period helps reduce risky behaviours.

Tip: Instead of smoking a whole joint or taking a puff every time it comes around, take a puff or two and then wait a few minutes. You may find a smaller amount is enough.

Not too often. Limiting how often we use helps reduce harms to ourselves and others over time.

Tip: Avoid using everyday or every weekend. Plan out the days and weekends you're not using so you don't spend your time sitting around and thinking about not using (e.g., spend time with a friend who doesn't use, go to the gym).

Only in safe contexts. Making informed decisions about where and with whom we use cannabis helps to minimize harms.

Tip: If going out, stay in the company of trusted friends and use safe transportation options.

Lowering the risks
  • Using a vaporizer is safer than smoking cannabis.

  • If smoking, take shallow puffs, not deep inhalations. Most of the THC is absorbed in the first few seconds, so you don't need to puff hard or hold your breath.


Is cannabis legal?

Cannabis is legal for adult use in Canada. Individuals 19 or older in BC may possess up to 30 grams of cannabis in a public place. Cannabis is regulated by the province of BC. Please visit: Please ensure you know where and when it is safe to use.


What to do if you or someone you know wants to explore change

For information on treatment options and resources throughout BC, call the Alcohol and Drug Information Referral Service at 1-800-663-1441. In Greater Vancouver, call 604-660-9382.

To better understand how substances play a role in your life, visit the You and Substance Use Workbook on the Here to Help website: This website also features detailed information on substance use and mental health.

You can also find information about a wide variety of substance use issues on the Canadian Institute for Substance Use Research, website:

About the author

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The Canadian Institute for Substance Use Research, formerly CARBC, is a member of the BC Partners for Mental Health and Substance Use Information. The institute is dedicated to the study of substance use in support of community-wide efforts aimed at providing all people with access to healthier lives, whether using substances or not. For more, visit


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