How cannabis affects you

Last revised: August 28, 2025

No use is an option but if you plan to use, learn how cannabis can affect you.

Short-Term Effects

Cannabis affects everyone differently, an individual can have different experiences each time they use cannabis. Some of the possible short-term effects include:

• Confusion
• Sleepiness
• Impaired ability to remember, concentrate, and pay attention
• Anxiety, fear, or panic
• Reduced coordination, reaction time, decision-making abilities, and ability to judge distances
• Paranoia, delusions, or hallucinations

Long-Term Effects

Long-term effects develop gradually over time with daily or almost daily (weekly) use. Long-term effects are worse for youth who start using frequently and early because the effects may not be fully reversible when cannabis use stops.

The long-term effects of cannabis on your brain can include an increased risk of cannabis dependency. Long-term cannabis use can harm your memory, concentration, intelligence, and your ability to think and make decisions.

Other long-term effects of smoking cannabis are similar to the effects of smoking tobacco. These effects can include risks to lung health, such as:

• Bronchitis
• Lung infections
• Chronic (long-term) cough
• Increased mucus buildup in the chest

Brain Development

Using cannabis before the age of 25 is associated with changes to the developing brain’s structure and function. Daily or almost daily (weekly) cannabis use can harm your short and long-term memory, thought patterns, focus and speech. This leads to difficulty with memory, concentration, intelligence, judgement, and decision-making. Reducing or stopping cannabis use may reverse some or all of these effects, and may help improve your long-term mental health and brain function.

Cannabis use can lead to mental health challenges

Using cannabis can increase the risk of experiencing psychosis and schizophrenia. The risk increases if you are a teenager, use regularly, or someone in your family has or had these conditions.

Cannabis use impairs your ability to drive safe

Cannabis can impair judgement, response time, attention and coordination. If you are 21 and under, there is a zero-tolerance law for impaired driving, meaning you cannot have any alcohol or substances (drugs) in your system. Plan a safe ride with a friend or use public transit and/or a ridesharing service.

Even small amounts of cannabis can affect your ability to drive safely. Learn what constitutes impaired driving and the potential penalties by visiting: Impaired driving | ontario.ca.

Cannabis smoke can be harmful to your lungs

Smoking/vaping cannabis produces harmful chemicals and carcinogens, similar to tobacco smoke. The chemicals are not in the cannabis plant but are created when the plant is burned. Over time, smoking/vaping cannabis can affect lung health, including:

• Bronchitis
• Lung infections
• Chronic (long-term) cough
• Increased mucus buildup in the chest

Cannabis use can lead to dependence

Regular use can lead to a cannabis use disorder or dependence. The risk for dependence is higher for individuals who use regularly and people under 25. If you become cannabis dependent it can be harder to reduce or quit. It can cause unpleasant feelings like:

• Irritability or anxiety
• Nausea and upset stomach
• Trouble sleeping
• Loss of appetite
• Sweating

Know where to go for help 

Signs you may need help with your cannabis or other substance (drug) use can include:

• Avoiding responsibilities at work, school, or home
• Giving up activities that you find important or enjoyable
• Using the substances (drugs) more often
• Feeling unable to reduce or manage your use
• Changes in mood (e.g., feeling irritable and paranoid)
• Changing friends
• Having difficulties with family members
• Not being open about how much or how often you use
• Changing sleep habits, appetite, or other behaviors

Don’t hesitate to ask for help if cannabis is impacting your life. If you need help, visit our Mental Health, Addictions and Substance Use Health Services and Resources webpage.