The Medical Cannabis Access Programme in Ireland1 currently provides access to cannabis to patients with one of three conditions when other treatments have been unsuccessful. The three conditions are spasticity (stiff and/or rigid muscles) associated with multiple sclerosis, nausea and vomiting associated with chemotherapy, and severe epilepsy.

An evidence review was conducted by the Health Research Board (HRB) to inform a Department of Health review of the current Medicinal Cannabis Access Programme on the suitability of cannabis-based products for medical conditions.

Findings

The HRB found evidence to support the use of prescribed medicinal cannabis for certain conditions for which it is currently approved in Ireland. These are nausea and vomiting in cancer and spasticity in multiple sclerosis. There was also evidence of a significant benefit for neuropathic or nerve pain, which can occur with conditions such as multiple sclerosis, diabetes, or spinal cord injury.

For most other conditions, including anxiety and pain in conditions such as cancer, rheumatic diseases, and fibromyalgia, there was no conclusive evidence to confirm the efficacy of prescribed medicinal cannabis.

Regarding the safety of prescribed medicinal cannabis, the review found that although serious adverse events do not appear to be common, there is some evidence that some side-effects such as dizziness, dry mouth, sedation, and headache can occur. Mixed evidence was found, however, on the likelihood of other adverse events such as drowsiness, nausea, and any psychiatric disorder adverse events. The HRB findings are similar to those reported by other overviews.

Methodology

The HRB review was an overview of reviews. While traditional systematic reviews gather evidence from existing original research studies (primary studies), an overview of reviews gathers evidence from existing systematic reviews. We focused on systematic reviews of studies of adults who received prescribed medicinal cannabis containing natural or synthetic cannabidiol (CBD) or tetrahydrocannabinol (THC) or their derivatives, and excluded evidence on cannabis for recreational use or for medicinal use without prescription/medical supervision.

The 47 reviews included systematic reviews covering research from the last 30+ years on a wide range of medical conditions. These included cancer, multiple sclerosis, rheumatic diseases, chronic pain, and mental health and neuropsychological conditions.

Conclusion

The evidence review revealed a fragmented body of research. Many types of medicinal cannabis exist, making it difficult to gather a strong body of evidence for one particular formulation for a given condition or complaint. Further high-quality research is needed based on randomised controlled trials. In the meantime, this review will help inform decision-making in relation to future policy on the use of prescribed medicinal cannabis along with input from patient groups, clinicians, and service planners.

The full text of the review is available for download on the HRB website.2

1    Department of Health (2020) Medical Cannabis Access Programme. Dublin: Department of Health. Available from: https://www.drugsandalcohol.ie/31653/

2    For further information, visit: https://www.hrb.ie/publications/