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Effects of cannabis

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"
  • less pain
  • feeling hungry
  • trouble concentrating or remembering things that just happened (short-term memory issues)
  • changes in judgment and 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 it was taken
  • 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:

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.

Mental health problems
Mental health problems include anxiety, depression, and psychosis. 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 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
  • 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 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.

Current as of: October 16, 2019

Author: Addiction and Mental Health, Alberta Health Services