You may have heard that cannabis might help to relieve symptoms of mental illness, including anxiety. But there is not enough evidence to say that it is safe or will work.
Medicinal cannabis should only be used as a last resort after other treatments have not improved symptoms, and after careful consideration of the risks and benefits.
Here are some important things to know about medicinal cannabis.
What is medicinal cannabis?
Medicinal cannabis is the term used for prescription medicines that contain cannabis. They are legal drugs in Australia and Aotearoa New Zealand.
These products contain one or more active ingredients extracted from the cannabis plant. The two most common are Tetrahydrocannabinol (THC) and Cannabidiol (CBD). THC is the psychoactive part of cannabis that produces a ‘high.’ CBD has no psychoactive properties.
They can be prescribed by health professionals if they think it may help relieve the symptoms of a range of health conditions including epilepsy, multiple sclerosis, chronic pain, insomnia, and mental health conditions.
Can medicinal cannabis be used to treat mental illness?
There is not yet enough evidence to support the use of medicinal cannabis to treat any mental illness or neurodevelopmental condition.
Medicinal cannabis may not improve your mental illness symptoms and could make them worse. There is not enough evidence to understand who may benefit from it and who it may harm. As this is a new treatment not well tested in research, evidence may change quickly over time.
If there is so little evidence, why is medical cannabis available?
Australia and New Zealand allows for the supply of non-smokable medical-grade cannabis products. There are currently no restrictions on the type of medical condition that it can be prescribed for.
Access to medicinal cannabis products in Australia and New Zealand is based on the idea that they have a low risk of harm, rather than evidence that they work.
Some people find that medicinal cannabis helps them, and some doctors will prescribe it if they think it will benefit you.
The use of medicinal cannabis for a person with a mental illness should preferably be part of a clinical trial. You can find information about clinical trials at the Australian New Zealand Clinical Trials Registry.
Is medicinal cannabis safe?
Side effects
Medicinal cannabis products can have short-term side effects such as disorientation, dizziness and confusion. Higher levels of THC in a product will lead to a higher chance of this type of side effect.
There is no research that has looked at the long-term side effects of using medicinal cannabis products.
Risk of psychosis
Using medicinal cannabis that has a lot of THC may increase risk of psychosis in young people whose brains are still developing. People with mental illness may also be at higher risk.
Products containing THC are not recommended if you have:
- a previous or current psychotic disorder
- an active mood or anxiety disorder.
Medical risks
Products containing THC are also not recommended if you:
- are pregnant, planning to become pregnant, or breastfeeding and/or
- have unstable cardiovascular disease.
Talk to your doctor about side effects and possible interactions with other medicines.
Who can prescribe medicinal cannabis?
Only doctors can prescribe medicinal cannabis products. Prescriptions should only be made after you have talked to your doctor about whether this treatment is right for you.
Psychiatrists are well placed to advise as they know about your mental health history, and possible side effects.
If you are considering using medicinal cannabis to treat a mental health symptom, you should:
- try evidence-based treatments first
- share your medical and psychiatric history with the prescribing doctor
- discuss side effects and interactions with other medicines, foods and illegal drugs
- be cautious of online/telehealth clinics offering fast turnaround prescriptions that may say medicinal cannabis works better than it does - and may not take account of all the risks
- consider enrolling in a clinical trial so that your physical and mental health can be closely monitored.
What other treatments can I use instead of medicinal cannabis?
There are a range of evidence-based treatments available to help you improve symptoms of mental illness.
For example, Cognitive Behavioural Therapy (CBT) is a treatment that has proven to work very well for anxiety, and other psychological therapies and medications can help too.
You should try these first, before considering medicinal cannabis.
What else should I be aware of?
Costs
Medicinal cannabis is expensive as it is not subsidised by governments.
Risks of self-medication with illicit cannabis
There is a difference between prescribed medicinal cannabis products and smokable or other illicit forms of cannabis. Self-medication is not advised, as it may worsen your mental illness symptoms. For example illicit cannabis may interact with medicines you are taking, or be stronger than prescribed cannabis.
Risks of smoking cannabis products
Smoking medicinal cannabis even if prescribed by a doctor or smoking illicit cannabis, is harmful to general health and lung health in particular.
Legal issues
Medicinal cannabis can affect your concentration or alertness, which can affect your ability to drive. The legal situation differs across Australian states and Territories and New Zealand and should be discussed with the doctor prescribing your cannabis.
Medicinal cannabis products prescribed legally in Australia and New Zealand may not be legal to take or possess in other jurisdictions.