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Mixing substances can have negative effects

Mixing substances can be a dangerous combination

Learn more about Polysubstance Use

Some young people think that cannabis is safer than alcohol, but survey results show that teens don’t typically use alcohol OR cannabis; they use both, at the same time.

Polysubstance use means taking two or more substances together at the same time. Whether the polysubstance use is intentional or unintentional, combining substances can have unpredictable and even dangerous side effects.

1 In 8 Canadians report mixing substances, and polysubstance use is more common among youth.1 Alcohol and cannabis are the most common combination of substances that are mixed together. 2 In 2022, two thirds of Canadians over age 16 who use cannabis reported mixing cannabis with alcohol: one in seven reports doing so either often or always. 3

The level of intoxication and side effects that an individual experiences can be unpredictable. Both substances have similar effects on the body and mind, including drowsiness, slowed reflexes and changes in judgment and time perception. Combining them can increase the effects of both drugs.

When cannabis and alcohol are used at the same time there is a greater likelihood of negative side effects occurring either physically or psychologically (panic, anxiety, and paranoia). 4 People who use cannabis and alcohol together tend to consume more of both, increasing the risk of overdose. 5

The order in which a person consumes these two substances also has an impact on the effects. 6

Alcohol before Cannabis

If a person drinks alcohol before using cannabis, the alcohol can increase the effects of THC, causing a person to feel more impaired than usual. Alcohol increases the absorption of THC, the main psychoactive ingredient in cannabis, which may cause anxiety, panic, or paranoia.

Cannabis before Alcohol

Using alcohol after cannabis may slow down the rise in blood alcohol levels, which can reduce the perceived effects of drinking, and cause people to drink more than usual, increasing the likelihood of alcohol poisoning. THC is also known to have antiemetic effects, which means it can prevent nausea and vomiting. However, if a person has drunk too much alcohol, cannabis can prevent them from vomiting, which can make the alcohol poisoning worse.

The use of both cannabis and alcohol or any other drug before driving can greatly increase the risk of getting into a car accident. 

Mixing cannabis with other substances or prescription drugs like sedatives or stimulants can lead to interactions that can be dangerous to a person’s health.7

Mixing alcohol with opioids, stimulants or prescription drugs can increase the risk of fatality due to overdose. These drugs can also complicate the effectiveness of naloxone used to reverse an opioid overdose, as naloxone only counteracts the effects of opioids.

When you have conversations with your kids about substances, discuss the negative impacts of mixing substances together. Ask them if they’ve ever been to a party where people have used a mix of substances and remind them that you are always there to help them out If it ever happens.

If you know someone who is already mixing drugs — intentionally or unintentionally — talk with them about the potential risks of health complications, overdose, and even death.

Get more facts about mixing medicine, alcohol, and street drugs at

  1. Government of Canada, 2022. Canadian Tobacco and Nicotine Survey, 2020
  2. Government of Canada, 2022. Canadian Tobacco and Nicotine Survey, 2020
  3. Canadian Cannabis survey 2022
  4. Cannabis information and support website
  5. American Addictions centre
  6. American Addictions centre
  7. Harvard Health Publishing – CBD and other medications
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