The first high quality study looking at the impact of cannabidiol oil on palliative care patients with advanced cancer found it did not improve their pain, depression, anxiety, or quality of life.
Palliative care is one of the conditions for which medicinal cannabis has been approved in Australia.
The trial, led by the Mater hospital and the University of Queensland, studied the effects of cannabidiol oil, also known as CBD, on the relief of pain, depression, anxiety and quality of life on 144 patients receiving palliative care for cancer. The trial was double-blinded, which meant neither the researchers nor the participants knew whether they were getting medicinal cannabis or a placebo.
All patients also received standard palliative care throughout the trial period.
“The trial found there was no detectable effect of CBD on change in physical or emotional functioning, overall quality of life, fatigue, nausea and vomiting, pain, dyspnoea or appetite loss,” lead author of the study and the director of palliative and supportive care at Mater, Prof Janet Hardy, said.
But she added that the study only examined the effect of CBD.
“The cannabis plant is very complex and contains a large number of cannabinoids and other compounds,” she said. “The two most prominent cannabinoids are CBD, which is cannabidiol, and THC, which is the one that makes you high when you smoke a joint.
“Our next study will look at a combination of CBD and THC to see if you need to have THC to get any benefit from medicinal cannabis. The problem with that is CBD is very popular because it doesn’t have the psychoactive effects. It means you can drive and do other activities while on it, whereas it’s illegal to drive on THC, whether it’s taken for recreational or medicinal purposes.”
CBD may also be useful for the treatment of cancer-related symptoms not examined in the study, she said, such as insomnia. Despite the lack of evidence of benefit, 36% of the study participants decided to buy a medicinal cannabis product after the trial, despite being unaware if they were taking the CBD or placebo. Hardy said it may be that CBD contributes to a greater feeling of general wellbeing, even if it did not improve specific symptoms.
Hardy said the study aimed to fill the gap in scientific evidence supporting the use of medicinal cannabis for pain relief and symptom distress due to cancer.
“The best way to describe the uptake of medicinal cannabis following its legalisation was as a social phenomenon,” she said.
“Everyone wanted it, but there was little evidence to guide its usage. Usually, new products entering the market have gone through extensive pre-clinical studies regarding best dosage and usage, however medicinal cannabis entered the market with very little guidance.”
The findings have been published in the Journal of Clinical Oncology.
A professor of pharmacology at Macquarie Medical School, Mark Connor, said “this might seem like a disappointing conclusion, but it’s an important one”. The study had found no adverse effects from CBD oil, he said, suggesting CBD is well tolerated and can be trialled on other patient groups with different conditions.
“A trial like this is certainly a stepping stone to potentially larger trials that may be designed in a way that can focus on more targeted areas where cannabinoids may have an effect, for example on more specific symptoms like insomnia, or even in specific types of cancers,” he said. “And what we can see from this study is CBD seems well-tolerated, and is unlikely to make things worse.”
