Anxiety, depression and post-traumatic stress disorder (PTSD) are of the most common mental health conditions for which Australians are prescribed medicinal cannabis.
Most recipes for mental health conditions, and for other conditions more broadly, it is for products containing higher levels of THC (tetrahydrocannabinol). This is the part of cannabis that causes a “high” and can affect thinking and mood.
Many of these recipes involve inhaled products such as dried leaves or flowers that people smoke or inhale.
This pattern of use – inhaling higher THC content for mental health conditions – appears to be partly driven by prescribing trends among 18- to 44-year-old men.
For stress alone, they exist almost three times more approvals for products containing the highest levels of THC than for products containing only CBD (cannabidiol).
But this prescribing pattern is inconsistent with the best available research. Most of the highest-quality clinical trials for anxiety have tested CBD-based products, not THC.
This is just one example of how Australians are using medicinal cannabis to treat mental health conditions without the best available evidence to support it.
Let’s start with anxiety
Anxiety is the the most common mental health reason people are looking for medicinal cannabis in Australia.
There is pop-up items CBD may help some people with anxiety, but findings are inconsistent.
The largest and most complete systematic review on medicinal cannabis and mental health found that it did not significantly improve anxiety symptoms. The authors said we still need larger, high-quality trials and studies that reflect how people use medicinal cannabis in the real world.
The evidence for THC is even more mixed. In our previous article we described how some people find THC makes them feel calmer, but others say it makes their anxiety worse. As few trials have investigated THC for anxiety, it is difficult to draw firm conclusions.
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Medicinal cannabis prescriptions have exploded in Australia, mostly for legal but unapproved products that we don’t even know work or are safe. In this series, experts tease what’s fueling the rise of medicinal cannabis, the consequences and what should happen next.
How about PTSD?
Evidence so far for the use of medicinal cannabis to treat PTSD is limited.
While some people report benefit, findings from the small number of high-quality randomized controlled trials (the gold standard for medical evidence) are mixed.
In a lot small studyonly five subjects completed the entire protocol. This vaporized cannabis test that contains either a combination of 10% THC and 10% CBD, or a product with primarily 10% THC.
Both products appeared to improve PTSD symptoms in the short term, but the trial had a problem recruiting participants. A larger study would be needed to know if the results are reliable.
Another test tried smoked cannabis with three contents: 12% THC, one containing mostly CBD, and one with equal amounts of THC and CBD. There was no change in PTSD symptom severity for either product compared to placebo. Smoking cannabis, including medicinal cannabis, is too not recommended due to its known defects.
Limited and uncertain evidence is one reason the Department of Veterans Affairs has decided not to fund medicinal cannabis for the treatment of mental health conditions, including PTSD;
What about depression?
There is even less high-quality evidence for the use of medicinal cannabis to treat depression. A recent systematic review found no relevant randomized controlled trials.
A small pilot study tested 150–300 milligrams of CBD per day alongside standard treatment for bipolar depression. CBD was well tolerated, meaning it didn’t cause serious side effects, but it didn’t help symptoms.
Studies on different types of depression are mixed. Some show potential benefits but also adverse effects including worsening symptoms or acute mental health effects such as psychosis, suicidal thoughts or anxiety. It is also unclear whether the adverse effects are due to the product or the underlying mental health condition.
Is medicinal cannabis safe?
Pop-up items shows that psychosis has been reported in people using medicinal cannabis containing higher levels of THC.
Australia’s medicines regulator, the Therapeutic Goods Administration (or TGA) he says Products containing THC are generally not suitable for people who have a personal or family history of psychosis or schizophrenia. This consideration also extends to people with past or current mood or anxiety disorders.
This is largely because THC can worsen or trigger symptoms in people who are already vulnerable to these conditions.
Why the increased risk?
Is this because of the THC or are these people already at higher risk? It’s probably a combination of both.
Daily or near-daily use of cannabis (which is common with medical use) connected with higher risk of psychosis or may contribute to its development.
Youth they may be particularly vulnerable to side effects after taking medicinal cannabis (and cannabis in general) for mental health conditions as their brains are still developing.
Other research shows that higher strength THC products appear to carry higher mental health risks for everyone. People who use frequently or for long periods are at further risk.
Thus, the picture that emerges is that the product used, how it is used and the individual matter and can influence health outcomes. Products with higher THC increase risks across the board, but those risks are increased in people who start young, use frequently, or continue long-term.
What happens when I stop taking it?
Some people whose mental health symptoms increase when they stop taking medical cannabis see it as proof that their drug worked. But this is not necessarily so. They may be experiencing withdrawal from cannabis.
Many people who use cannabis (medicinal or otherwise) experience improvement in symptoms – such as worry or sleep difficulties – when they stop. This may be very similar to the symptoms that prompted them to seek treatment.
We also know around us one in three or four people those who use cannabis for medical purposes will develop a dependence on cannabis and are likely to experience withdrawal symptoms if they suddenly stop using it.
So cannabis withdrawal may be more common than people think and may well explain symptoms that occur when someone stops taking it.
How do I know what is right for me?
Many studies looking at whether medicinal cannabis could help different mental health conditions are of low quality or have conflicting findings. So the evidence is not yet strong enough to recommend it as the best treatment for any mental health condition.
So talk to your trusted, regular doctor to help you weigh the potential benefits and risks of medicinal cannabis, especially if you have a history of mental health concerns.
Given the mixed evidence and the TGA’s warnings, it’s really important to seek individualized medical advice.
If you or someone you know is struggling with anxiety, mood swings or any mental health concerns – whether they are related to cannabis use or not – the following support is available: Beyond Blue (24/7 support): 1300 22 4636 and Lifeline (crisis support): 13 11 14.
