When not to use medicinal cannabis

As with all medical treatments, medical cannabis is not for everyone.

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As with all medical treatments, medical cannabis is not for everyone. The risk of harm from medical cannabis can outweigh the potential benefits for some groups of people. Experts use scientific research to find out which conditions increase the risk of harm from medical cannabis.

Furthermore, in Australia medical cannabis is not a first-line treatment for any condition. This means that doctors only use medical cannabis for people who have tried several other medicines without success.

History of Psychotic Illness

Medical cannabis is not safe for people who have a personal or family history of certain mental health conditions, such as:

  • Psychotic illnesses e.g. schizophrenia
  • Mood disorders, e.g. depression
  • Personality disorders
  • Severe anxiety disorder

Cannabis has effects on the brain that can make these conditions worse. Ask your doctor for more information on medical cannabis and mental health.

Serious Heart Disease

Medical cannabis is not safe for people with serious heart disease, such as:

  • Ischemic heart disease
  • Arrhythmias
  • Poorly-controlled hypertension
  • Severe heart failure

If people with these conditions take cannabis, it can stress the heart and increase the risk of having a heart attack.

If You Are Pregnant or Breastfeeding

Women who are pregnant or are planning to become pregnant should not use medical cannabis. Tests in animals have shown that cannabis can harm the developing baby.

In addition, cannabis can pass into a woman’s breast milk at high concentrations; this can harm the breast-fed infant. Women who are breastfeeding should avoid medical cannabis.

Driving and Operating Machinery

People who use medical cannabis can experience dizziness, fatigue and concentration problems as side effects. This makes it difficult to carry out skilled tasks and can impair judgement. People who need to drive or operate dangerous machinery should not take medical cannabis as they are at higher risk of having an accident


A small number of people are hypersensitive to cannabis or other ingredients in medical cannabis products. These people should avoid using medical cannabis as it can cause a severe allergic reaction.

Seizures (THC vs CBD)

Scientists are looking into the potential of a cannabis compound called cannabidiol (CBD) for treating some severe types of childhood epilepsy. However, in animal tests, another compound in cannabis called tetrahydrocannabinol (THC) was found to cause seizures. People with a history of epilepsy or seizures should talk to their doctor about the safety of different types of medical cannabis.


Please note: this reference material is informational and does not constitute as advice. Furthermore, the information you are being referred to may not comply with the Australian regulatory environment. GreenChoices recommends any information provided should be discussed with a healthcare professional and does not replace their advice.

  1. https://www.tga.gov.au/sites/default/files/guidance-use-medicinal-cannabis-australia-overview.pdf
  2. https://www.tga.gov.au/sites/default/files/auspar-nabiximols-130927-pi.pdf
  3. https://www.ncbi.nlm.nih.gov/pubmed/26886465
  4. https://www.hindawi.com/journals/jt/2009/596149/