Health Information and Tools > Health A-Z >  Cannabis: Effects of cannabis
Facebook Tweet Share

Main Content


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"
  • feeling hungry
  • trouble concentrating or remembering things that just happened (short-term memory issues)
  • changes in judgment 
  • 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 you used it (like smoking it, vaping it, or eating it)
  • 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.​

Fertility problems
Cannabis use may make it harder for you to have a baby. Using cannabis can cause menstrual cycle changes and increases the risk of testicular cancer, which can lead to low sperm count and quality.

Mental health problems
Cannabis use can make the symptoms of anxiety, depression, and bipolar worse. It can also increase your risk for thoughts of suicide and suicide attempts. Using cannabis can also increase your risk for psychosis (seeing or hearing things that are not real) and developing schizophrenia. 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 tetrahydrocannabinol (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 or almost every day​
  • use products with high levels of THC
  • 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 may 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.​

Learn more about CHS, how to care for yourself, and when to get help.

If you’re worried about your own or someone else's use of cannabis, alco​hol, or another drug, call Health Link at 811 or the Addiction Helpline at 1-866-332-2322.


Current as of: July 25, 2023

Author: Addiction and Mental Health, Alberta Health Services