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Marijuana (Cannabis) Centre for Addiction
and Mental Health

About Marijuana

Marijuana, hashish (hash) and hash oil come from cannabis sativa, a type of hemp plant. All three contain THC, a chemical that changes the way you think, feel and act. The word “cannabis” is used to refer to all three.

  • Marijuana is made from the dried leaves and flowering tops of the plant.
  • At a certain stage in the growth of the plant, before the flowers are mature,they become coated with a sticky resin. The resin can be dried to make hash.
  • Hemp can also be used to make rope, fabric and paper. When it is grown for this purpose, the amount of THC is too small for someone to use it to get high.

What does marijuana look like?

  • Marijuana is a green, brown or grey mixture of dried and shredded hemp leaves, stems, seeds and flowers.
  • Marijuana is often rolled in paper so it looks similar to a cigarette. A common slang name for this is a joint.
  • Hash is dark brown or black, and comes in solid chunks.
  • Hash oil is reddish-brown or green.

Street names:

Weed, herb, chronic, jay, bud, blunt, bomb, doobie, hydro, sinsemilla, hash, joint, pot, grass, reefer, Mary Jane (MJ), ganja, homegrown, dope, spliff

Did you know?

Cannabis sativa, cannabis indica and cannabis ruderalis have all been used for their intoxicating effects. When grown for industrial purposes, cannabis indica contains very little THC and could not be used to get high.

Who uses marijuana?

  • Marijuana is the most commonly used illegal drug in Canada.
  • Almost half (44%) of Canadians say they have used marijuana at least once in their lifetime.
  • In 2005, just over one-quarter (26.5%) of Ontario students (grades 7–12) said they had used marijuana in the past year, and one-third (31%) reported trying it at least once in their lifetime.
  • In Ontario, male students are more likely to use marijuana than females (28% versus 25%).
  • Students’ rates of marijuana use vary across Ontario: Toronto students are less likely to use it (20%) than students in the north (33%) or west (29%).
  • Three per cent of Grade 7 students have tried marijuana in the past year.
  • By the time they have reached Grade 12, nearly half (46%) of Ontario students have used marijuana in the past year.
  • About one in eight students (12%) who use marijuana use it every day. This is about three per cent of all grade 7 to 12 students in Ontario (about 33,200 students).

True or False?

  1. Marijuana is natural, so it can’t be bad for you.
  2. All marijuana is the same strength.
  3. One in five students (20%) who drive say they have driven within one hour of using marijuana.


  1. False. A lot of natural things are poisonous, like snake venom and certain plants. When you smoke marijuana, it releases harmful chemicals into your lungs.
  2. False. There is great variation in how strong marijuana can be.
  3. True. And what many people don’t know is that if you drive while you are high, you will be impaired.

Marijuana and its effects

Can you get addicted to marijuana?

Yes, you can. Some people have a hard time quitting and have to find treatment.

They may feel they need the drug, and get anxious when they don’t have any.

Some people who use a lot of marijuana every day and then quit suddenly may have problems sleeping. They may get anxious, irritable or nervous without the drug. Or they may have an upset stomach or lose their appetite. These symptoms rarely last more than a few days.

Is marijuana harmful?

Yes. If you smoke marijuana, it can harm you. Many people don’t know this, but marijuana smoke contains more tar and more of some cancer-causing chemicals than tobacco smoke.

Here are some other ways that marijuana use can harm you:

  • To get the maximum effect, people who smoke marijuana often inhale more deeply and hold the smoke in their lungs longer than tobacco smokers do. This increases the risk of cancer.
  • Smoking marijuana irritates your lungs and has been linked to chronic cough and bronchitis. It may also make asthma worse.
  • In people at high risk of developing schizophrenia, marijuana may bring on symptoms earlier.
  • If you're pregnant, the more marijuana you smoke, the more likely your baby will have problems (such as being too small).
  • Using a lot of marijuana for a long time may make it harder to pay attention, remember things and learn.
  • Large doses of marijuana can lead to “toxic psychosis.” This can cause people to hallucinate (see or hear things that aren’t really there), become paranoid (feel like people are out to get them) and believe things that aren’t true. These symptoms usually disappear within a week after the person stops using marijuana.
  • Marijuana that you buy illegally may contain other drugs, or harmful pesticides or fungus.
  • You may make decisions while using marijuana that you regret later.
  • Marijuana affects your co-ordination and makes it harder to concentrate and react. This makes it dangerous to do things like ride a bicycle, drive a car or operate machinery.

Fast facts

There are at least 400 chemicals in marijuana.

Did you know?

If you smoke marijuana, the effects last for several hours. But the THC (the main active ingredient) is stored in your fat cells and can stay in your body for days or weeks! This doesn’t mean that you would be high for weeks, but you would test positive on a drug test for THC weeks after you smoked marijuana.

How does marijuana make you feel?

Marijuana affects each person differently. How it affects you depends on:

  • how much you use
  • how strong it is
  • how often you use it
  • whether you smoke it or eat it
  • your mood and what you expect to happen when you take it
  • whether you have drunk alcohol or used other drugs when you take it.

If you use marijuana, you may:

  • feel more relaxed and less inhibited—or more anxious, confused, panicky or even paranoid
  • be more outgoing and talkative, and laugh more—or you may be quiet and withdrawn
  • find that time seems to pass more slowly and distances become distorted
  • have keener senses, such as sharpened hearing and vision
  • have trouble keeping your balance
  • have trouble thinking clearly, remembering things that just happened, and doing some tasks (e.g., homework)
  • want to eat a lot (get “the munchies”)
  • have a sore throat and lungs
  • have increased heart rate
  • feel sleepy as the drug wears off
  • hallucinate, especially if you use a lot of marijuana at one time
  • have a dry mouth and/or red eyes.

The dangers, medical uses, and the law

Is it dangerous to smoke marijuana and drive?

Yes. Marijuana makes it harder to concentrate, pay attention and tell how far away things are, for up to five hours after you use it. It also makes your hands less steady and slows your reaction time; this means you wouldn't be able to react as quickly to a sudden, unexpected emergency. Your risks go up when you combine smoking marijuana with drinking alcohol. All these things may make it harder to drive safely. There is no roadside breathalyzer test for marijuana. But specially trained police can tell if you are high, and you could be charged.

Are there medical uses for marijuana?

Yes. Research has shown that marijuana can relieve nausea and vomiting, and can help a person regain his or her appetite. This can be helpful for people with AIDS or those undergoing cancer treatment. Synthetic THC is used as a prescription medicine for people in these situations. Marijuana may also help relieve pain and reduce muscle spasms - but more research is needed to see how useful it is for these problems.

Fast facts

Health Canada has allowed some people with serious illnesses to grow marijuana for medical use. This is called a medical exemption.

Did you know?

Research shows that you have a greater chance of having a car crash when you drive after using marijuana. After alcohol, marijuana is the second most common drug found in dead and injured drivers.

Did you know?

Mixing marijuana and alcohol is more dangerous than using each drug separately. Mixing even small amounts of marijuana and alcohol can make it dangerous to drive. Many impaired drivers test positive for marijuana and alcohol together.

Can smoking marijuana affect my school performance?

THC remains in your brain for days or weeks, and may affect your memory, speech and learning. Using marijuana regularly also affects your thinking and can make you less motivated.

Is marijuana legal?

No. Marijuana possession is illegal in Canada. A first-time conviction for possessing 30 g or less of marijuana can result in a six-month prison sentence, a $1,000 fine or both. You will also have a criminal record, which may make it harder to get some jobs or to travel to another country. The maximum penalty for a second offence is a $2,000 fine and 12 months in prison. A change has been proposed in the law about possessing marijuana. The legal penalty for possession of small amounts would be reduced to a fine with no criminal record. Some people call this “decriminalization,” but possessing marijuana would still be illegal.

Fast facts

  • Most people convicted of possessing marijuana for the first time receive a fine or a discharge. Either way, you could end up with a criminal record.
  • The maximum penalty for growing marijuana is seven years in prison.
  • The maximum penalty for selling marijuana (called “trafficking”), or bringing it in or out of the country, is life in prison.

Did you know?

When you smoke marijuana, you risk getting arrested. In 2003, more than 41,000 Canadians were arrested for marijuana possession.

Reducing risks and getting help

How can I reduce my risks?

  • Don’t drive when you are high. To reduce risk even more, don’t drive for several hours after using marijuana.
  • Don’t get into a car with someone who has been using marijuana.
  • Don’t mix marijuana with alcohol or other drugs.
  • Don’t use marijuana before or during school.
  • Understand that smoking marijuana could get you arrested.
  • Choose not to use marijuana.
  • Get help if you think your marijuana use is getting out of control.

How can I get help?

Do you, a family member or a friend have a problem with substance use? If you want help, you may want to talk to someone you trust, such as your doctor, a teacher, a health nurse, or a guidance or addiction counselor. You might also want to contact an addiction assessment centre or a self-help group (look in the Yellow Pages of your phone book under “Addictions”). Here are some other places to look for help:

  • Centre for Addiction and Mental Health’s Information Centre at 1 800 463-6273
  • Kids Help Phone at 1 800 668-6868
  • Ontario Drug and Alcohol Registry of Treatment at 1 800 565-8603 or

About marijuana

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