About Marijuana

Marijuana is the most widely used illegal drug among youth today.

Teenagers and their parents or guardians are often unaware of the many mental and physical health risks linked to marijuana use. In fact, today's marijuana is stronger than marijuana from many years ago. The use of this stronger type of marijuana can contribute to increased health risks. While the dangers of marijuana use affect people of all ages, young people are especially vulnerable.

Learn more about the health risks of marijuana use.

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What is marijuana?

Marijuana (also known as pot, hash, Mary Jane, and weed) comes from the Cannabis plant. The active ingredient in marijuana and other products from the Cannabis plant, such as hashish and hash oil, is a substance known as tetrahydrocannabinol (THC).

Marijuana generally refers to the dried leaves and flowers of the plant, but it may also contain seeds and stems. Its colour ranges from green to grayish-green to brown. Marijuana smoke often has a pungent or spicy smell to it.

Marijuana is usually smoked in hand-rolled cigarettes, wrapped in cigar tobacco or put in pipes or water pipes. It can also be cooked and eaten.

Hashish is made from cannabis plant resin that has been pressed. Its colour ranges from green to blonde to brown to black. It may be soft and pliable or firm and brittle. Hashish is generally smoked, but can be eaten. It usually contains more THC than marijuana.

Hash oil is also produced by extracting resin from the plant. Its colour ranges from gold to red to dark brown. Hash oil is usually a thick, sticky liquid. It is typically added as drops to a joint or cigarette and then smoked. It usually contains more THC than marijuana.

How does marijuana work?

Today's marijuana is much stronger than marijuana from many years ago. Studies show that the average level of THC, the principal "mind-altering" component of marijuana, has increased by 300% to 400% over the last few decades.

When marijuana is smoked, the THC in the smoke passes quickly from the lungs into the blood. Because blood is always travelling through the body, THC soon reaches the brain. Within a few minutes, the drug produces several short-term effects.

These short-term effects can last up to 8 hours after smoking or 12 hours or longer if the marijuana is eaten.

How does marijuana affect you?

Many of the harmful physical and mental effects of marijuana are known. But marijuana use can also come with effects the user did not expect or want.

Unexpected or unwanted effects

Marijuana can have unexpected or unwanted effects. Instead of feeling calm and happy, some people may experience other effects such as:

  • nervousness,
  • anxiety or panic,
  • mild paranoia, or
  • hallucinations and delusions.

Youth are especially vulnerable to the health effects of marijuana use, including harmful effects on mental functioning, and psychosis and schizophrenia.

This is because adolescence is a critical time for brain development. THC targets a system in the brain that plays an important role in the way the brain develops and works. Having THC in the brain at such a critical time can therefore interfere with brain development and harm brain function. It can also increase the risk of triggering a psychotic episode or a mental illness such as schizophrenia.

Mental effects

Regular long-term marijuana use can harm concentration, cause loss of memory, harm the ability to think and make decisions, and decrease IQ. Some of these effects may persist after stopping marijuana use.

Marijuana use that begins early in adolescence, that is frequent and that continues over time has been associated with an increased risk of psychosis and schizophrenia. The risk is greatest in individuals with a personal or family history of such mental illnesses.

Did you know?

Marijuana use that begins early in adolescence, that is frequent and that continues over time can lead to addiction. It is estimated that 1 in 9 marijuana users will develop an addiction to marijuana. Learn more about marijuana addiction.

Physical effects

In terms of physical effects, the drug:

  • expands the blood vessels in the eyes, making them look red,
  • relaxes and enlarges the airways leading to the lungs,
  • lowers blood pressure, and
  • can double normal heart rate.

Marijuana smoke irritates the throat and lungs, causes coughing, and is associated with symptoms of bronchitis. Marijuana smoke also contains many of the same cancer-causing materials as tobacco smoke.

An increased heart rate can put a lot of stress on the heart.

When the drug wears off, the user may have difficulty sleeping or feel:

  • irritable,
  • anxious,
  • hungry, or
  • depressed.

These short-term effects can be felt even if marijuana is used infrequently.

Did you know?

Marijuana contains hundreds of substances, some of which are psychoactive and can affect the proper functioning of the brain and body. Learn more about the health risks of marijuana use.

The science is clear

Marijuana use equals health risks.

  • Marijuana use can impair your concentration, your ability to think and make decisions, and your coordination. This can affect your motor skills, including your ability to drive.
  • Marijuana use may increase anxiety and cause panic attacks, and in some cases cause hallucinations.
  • Marijuana is not an approved drug or medicine in Canada. Possession and use of marijuana remains illegal in Canada unless authorized by a health care provider.

Get help

Are you struggling with drug abuse? Is someone you care about having a problem?

Help is available, whether you need it for yourself, a friend, or a family member.

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