When considering cannabis as a therapeutic option, some groups of patients should be cautious or even avoid administration of cannabis.


The use of cannabis during pregnancy should be avoided. Cannabinoids will reach the foetus through the umbilical cord and may slow foetal growth and affect the development of the nervous system. Cannabis should also be avoided during breastfeeding, as it is detected in breast milk1.

Combination with other CNS depressant substances

When using cannabis in combination with other substances that have a depressant effect on the central nervous system (CNS) – such as alcohol, benzodiazepines and opiates – there may be an additive tranquillizing effect2,3.


Cannabis, especially with a high THC content, should not be used by anyone under the age of 25 unless the benefits outweigh the risks, as the use of cannabis in this patient group can affect the way the brain matures and lead to long-lasting effects on cognition and an increased risk of psychotic disorders and dependence3,4.


Data on the use of cannabis by elderly patients are very limited. Age-related factors, such as reduced balance, slower metabolism by the liver and cardiovascular diseases, should be considered when administering cannabis to this patient group3.

Psychiatric disorders

Patients with a personal history of psychiatric disorders (particularly psychosis and schizophrenia, but also mood disorders) or a familial history of schizophrenia should be cautious when using cannabis products, particularly with a high THC content. Care should also be taken in the case of patients with a history of abuse of alcohol, medicines or illicit drugs, as the risk of cannabis abuse for these individuals is higher3,5.

Cardiovascular diseases

THC may cause tachycardia (accelerated heart rate) and orthostatic hypotension (low blood pressure when standing up). Caution should also be exercised for patients with pre-existing cardiovascular diseases2.

Liver or renal diseases

Patients with severe liver or kidney impairment should exercise caution when using cannabis, as there is a lack of data on the potential accumulation of cannabinoids due to chronic usage3.


1. Grant, K. S., Petroff, R., Isoherranen, N., Stella, N. & Burbacher, T. M. Cannabis use during pregnancy: Pharmacokinetics and effects on child development. Pharmacology and Therapeutics vol. 182 133–151 (2018).

2. Information for pharmacists and healthcare professionals. (2021).

3. Health Canada. INFORMATION FOR HEALTH CARE PROFESSIONALS. Cannabis (marihuana, marijuana) and the cannabinoids. (2018).

4. Felice, M. de & Laviolette, S. R. Reversing the Psychiatric Effects of Neurodevelopmental Cannabinoid Exposure: Exploring Pharmacotherapeutic Interventions for Symptom Improvement. International Journal of Molecular Sciences 22, (2021).

5. Lowe, D. J. E., Sasiadek, J. D., Coles, A. S. & George, T. P. Cannabis and Mental Illness: A Review. European archives of psychiatry and clinical neuroscience 269, 107 (2019).