If you start using cannabis in your teens, if you use cannabis more than a few times a week, or if you take very high doses of THC and low doses of CBD, you are at risk of serious mental health problems. These include: anxiety and depression, and psychotic disorders including schizophrenia and bipolar disorder, and cannabis dependency. For more information on how to reduce your risk, please visit the Lower-Risk Cannabis Use Guidelines.

Anxiety and depression

Research has shown that teenagers with high levels of anxiety might start using cannabis at a younger age, and they may increase the amount and frequency of use more quickly than other teens. Teen girls who experience depression may also use larger amounts of cannabis more often than peers. 

Frequently using cannabis to self-medicate for anxiety and depression, rather than developing healthy coping skills, can make it more difficult to recover from these problems.

There is conflicting evidence about cannabis and its effectiveness to treat anxiety. If you are using or considering trying cannabis to treat your anxiety or depression, speak to your health care provider.

Psychotic disorders

It is not recommended to use cannabis if you have a personal or family history of psychosis, schizophrenia, or bipolar disorder.

Most cannabis users will not develop schizophrenia, but for those already at risk of developing schizophrenia, either due to family history or other risk factors, cannabis can increase this risk. This is especially true if cannabis use starts when a person is young, or if a person uses cannabis frequently.

Chronic symptoms of psychosis may also appear when cannabis is used frequently or from an early age. These can persist even after cannabis use has stopped. This may not occur in every cannabis user, but using cannabis for long periods of time greatly increases a person’s risk.

For conditions like bipolar disorder, where periods of mania or psychosis may be triggered, cannabis increases the likelihood that these manic periods will occur.


Addiction (or dependency) to any drug is a serious and often relapsing chronic disease. Cannabis use disorder is “a problematic pattern of cannabis use leading to clinically significant impairment or distress.”1 Dependency happens in about nine per cent of cannabis users, compared to alcoholism, which occurs in 23 per cent of users. People who have a cannabis use disorder can have a difficult time quitting or cutting back on use, or may experience withdrawal symptoms if they do. Withdrawal symptoms include anxiety, irritability, upset stomach, loss of appetite, disturbed sleep and depression.2

Signs of dependency include:

  • craving cannabis
  • not completing important responsibilities at work, school or home;
  • giving up important social or occupational activities
  • using cannabis more often or in larger amounts to achieve the desired effects
  • having difficulty cutting down on or controlling cannabis use

If you or someone you know is struggling with a dependency, contact the youth addictions centralized intake service: 1-877-710-3999, or the Manitoba Addictions Helpline at 1-855-662-6605.

1Diagnostic and Statistical Manual of Mental Disorders, DSM-5.
2Canadian Nurses Association, p. 7.