A growing enthusiasm for medical cannabis — especially among patients with serious life-threatening conditions — has been coupled with growing evidence to support the benefits for medical cannabis for a variety of symptoms. Recent reviews and meta-analyses have pointed to benefits for treating pain, nausea, anorexia, spasticity, and several other symptoms.
However, is difficult to guide clinicians and patients in choosing the optimal ratio of tetrahydrocannabinol (THC) and cannabidiol (CBD). These molecules have different receptors, physiological effects, and potential medical benefits. THC is associated with psychoactive effects, such as euphoria, anxiety symptoms, paranoia, and hallucinations, whereas CBD is not.
A team of researchers, led by David J. Casarett, performed a record-based retrospective cohort study of 2,431 patients in Canada. The team reported that there are current results that may be clinically useful and which should prompt future research.
The study's results "offer a unique view of real-world medical cannabis use and identify several areas for future research."
• The results underscore the importance of the THC:CBD ratio as an important attribute. This is particularly true for neuropathic pain, insomnia, and depressive symptoms, for which this ratio seems to explain considerable variance in perceived effectiveness. For neuropathic pain, an increase in THC:CBD ratio over the full range (0-100%) more than doubled perceptions of effectiveness. There is increasing evidence that CBD offers benefits in the treatment of neuropathic pain, and some suggestion that CBD-only formulations may be effective.
• Some symptoms may not be as responsive to increases in the THC:CBD ratio. For post-traumatic stress disorder-related flashbacks and anorexia, the evidence to support the use of cannabis is still very light.
• For anxiety symptoms, increases above a ratio of 1:1 were associated with reduced effectiveness: one well-recognized side effect of THC is anxiety symptoms, sometimes accompanied by paranoia.
• The results did not indicate that a higher THC:CBD ratio is associated with greater effectiveness in the treatment of anorexia. Thus, the results suggest that CBD may also have a role to play in the treatment of anorexia.
Although these results make valuable suggestions for future research, three limitations should be considered in interpreting the results.
- This study relied entirely on patients' reports of their own symptoms: errors in diagnostic classification would tend to reduce the ability to detect differences in the association between THC:CBD ratio and perceived effectiveness across symptoms.
- Additional data about patients was limited: the etiology for a patient's report of neuropathic pain or anorexia was undefined.
- The study may overestimate THC's value because of the placebo effect.
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Adapted from Casarett DJ, Beliveau JN, Arbus MS, Sanders JJ et al. Benefit of tetrahydrocannabinol versus cannabidiol for common palliative care symptoms. Journal of Palliative Medicine Vol. 23, No. 1. Internet. Available at https://doi.org/10.1089/jpm.2018.0658 Accessed on January 22, 2020.