Youth Marijuana Use - What Parents Should Know

Sheena Gereghty, PhD

Knowledge Broker, Canadian Centre on Substance Abuse

As a parent, do you worry about your teen using marijuana?

If you are nodding your head in agreement right now, rest assured you are not alone.

Many parents worry about marijuana use, especially in youth (up to mid-20 years of age). Of course, worrying will not change anything. But talking with your teen about marijuana can.

Use the facts below to kick start a good conversation with your teen. Then keep the lines of communication about drugs open.  

Why do youth use marijuana?

Conversations with young people across Canada told us that some view marijuana as a natural, harmless substance. They feel that using it is exciting, and it helps them enjoy parties and understand things differently. Youth may also use marijuana to avoid feeling left out by friends who are using it, to cope with problems or simply because they are bored.

While some teens may argue that marijuana use is "no big deal," the reality is far from it. In 2013, about a quarter (25 per cent) of all Canadian youth used marijuana. If you suspect your teen may be among the 25%, a conversation might be a good first step in uncovering why they are using it and what they think about marijuana. 

It is also important to help your child understand the truth behind common myths. But this can be difficult to do without the facts - the evidence.

To help you have these chats with your son or daughter, we have brought together some of the key facts about marijuana based on the latest research evidence.

How does marijuana affect the brain?

The human brain continues to develop into our twenties. Our bodies have a system - called the endogenous cannabinoid system - that helps to make sure the brain develops properly. When a young person uses marijuana, it floods this system and prevents it from working as it should. Use of marijuana can lead to changes in the brain structure, and how a young person thinks and feels. These harms are the most severe in youth who begin using early (during or before adolescence) and/or those who use regularly (daily or almost daily). 

Is it safe to drive after using marijuana?

No. Some youth believe that using marijuana makes them better drivers. In fact, the opposite is often true. Drivers who use marijuana are less able to pay attention to more than one thing and have slower reaction times. These changes can make it difficult for drivers to deal with common situations - for example watching the traffic lights - while scanning for other cars and pedestrians.

It is also illegal drive under the influence of marijuana. What many don't realize is that police officers can detect drivers impaired by marijuana and, importantly, drug-impaired driving carries the same penalties as drunk driving. Even if your child is not driving, make sure he or she knows the dangers of riding as a passenger with a driver who has used marijuana.

What are the long-term risks of using marijuana?


Daily and early marijuana use can cause changes in the brain that affect how a young person thinks and behaves. These changes can appear as poor performance in school and lower test scores. Studies of regular marijuana users revealed they were less likely to complete high school or obtain post-secondary degrees or diplomas. Youth who use marijuana have changes in the size of certain areas of their brains that suggest the connections in their brains are less effective than in those of youth who do not use marijuana. These changes affect areas responsible for motivation, risk-taking, understanding and decision making. The brains of young people who use marijuana and have these changes have to work harder to complete tasks than the brains of those who do not use it. 

Mental health

Adolescence is a time when both mental illness and substance abuse can develop. There is an important link between mental health concerns and marijuana use. Research findings have suggested that marijuana use might have negative effects on youth who are at risk for mental illnesses. For example, marijuana use is related to early onset of psychosis (sensing events that are not really occurring) and is a risk factor for developing schizophrenia (experiencing psychotic symptoms and having disturbed behaviours and difficulty thinking). Marijuana use can also worsen the symptoms of schizophrenia, depression and anxiety for youth already dealing with these concerns. 


Another common but incorrect belief held by youth is that marijuana isn't addictive. The fact is that one out of every six youth who use marijuana during adolescence will develop dependence. Whether a person develops a marijuana use disorder depends on many factors such as other drug use, recent life events, gender and, importantly, his or her relationship with parents.

Common symptoms for marijuana dependence include:

  • Wanting to use all the time;
  • Using even when a person didn't plan to;
  • Spending a lot of time getting or using marijuana;
  • Needing a greater amount of marijuana to get the same effects; and
  • Continuing to use marijuana even though it is causing physical or social problems.

If you recognize any of these symptoms in your child, speak to your doctor or nurse. Treatments are available and are most effective if they start early, include family members and address mental health concerns.

How can marijuana be harmful if it's used as a medication?

Research on the use of marijuana to treat certain medical conditions is developing. While some people might use medical marijuana, this does not make it safe for youth. Prescription drugs can be harmful if used in a different way than they were prescribed (such as the amount used or how it is taken) or if taken by someone that it was not prescribed to. In the same way, marijuana can still cause harm. Marijuana produced for medical purposes can be quite different from the marijuana a young person might get. In addition, marijuana used for recreational purposes can contain other dangerous substances.

Is marijuana use illegal?  

Right now, it is illegal to grow, have or sell marijuana. Punishment can range from paying a fine to going to prison. Remember, it is also illegal to drive under the influence of marijuana. Drug-impaired driving has the same penalties as drunk driving.


There is a lot that we still don't know about the effects of marijuana use. We do know that early and regular use results in the greatest harms. Talk with your child. Encourage him or her to avoid, reduce and delay using marijuana.    


Do you have more questions?

Contact Us