Cannabis for Medical Purposes

Last revised: August 28, 2025

Ottawa Public Health provides information on the health effects from using cannabis so residents can make informed decisions. Ottawa Public Health recommends that anyone who is considering the use of cannabis for medical purposes talk with a health care provider.

Prescription cannabinoids (nabilone and nabiximols) are approved therapeutic drugs in Canada. Dried and fresh cannabis and cannabis oil are not approved as therapeutic drugs by Health Canada as current research does not establish their safety and effectiveness.

The evidence on cannabis for medical purposes continues to emerge. Some research shows that the CBD (cannabidiol) found in cannabis may help treat specific medical conditions. The College of Family Physicians of Canada has published a simplified guideline for prescribing medical cannabinoids in primary care. A summary of the findings and guidelines is available.

Concurrent Disorders – Mental Health and Cannabis

• Mental illness and problems occurring with substance use often occur at the same time. Having one can increase the risk of developing the other.
• Regular cannabis use can increase the risk of experiencing psychosis and schizophrenia. The risk is higher for individuals who:
  • Start using cannabis in adolescence
  • Have a personal or family history of psychosis or schizophrenia
  • Use high-potency cannabis products
• Some people with mental illness report using cannabis to help cope with their symptoms such as anxiety or depression. However, cannabis use may worsen mental health symptoms over time.
• There is increasing evidence linking frequent cannabis use to depression and anxiety, particularly among young people.
• If your client or someone in their family has a history of mental illness or a substance use disorder, it is best to avoid using cannabis. For individuals seeking support with managing stress, anxiety, or other mental health and/or substance use health challenges, visit our Mental Health, Addictions and Substance Use Health Services and Resources webpage.

Lower-Risk Cannabis Use Guidelines (LRCUG)

The Lower-Risk Cannabis Use Guidelines (LRCUG) are an evidence-based tool that allows people who use cannabis to modify and reduce their risks for health harms associated with cannabis use based on evidence-informed recommendations. Make an informed decision about cannabis use. No use is an option but if you plan to use, follow these tips: lower-risk cannabis use tips.

For more information on resources and services, visit our Mental Health, Addictions and Substance Use Health Services and Resources webpage