Medicinal cannabis study offers mixed findings on benefits

Medicinal cannabis is used for conditions such as spasticity associated with multiple sclerosis, intractable nausea and vomiting associated with chemotherapy, or severe treatment-resistant epilepsy.

A new study by Ireland’s Health Research Board (HRB) has found some evidence to support the use of prescribed medicinal cannabis for certain conditions.

But the agency found a general lack of quality in primary studies and reviews, which it said made it very difficult to draw “well-founded conclusions about the relative benefits (or lack thereof) of medicinal cannabis” for any given health condition.

The study was conducted to inform a Department of Health review of the current Medicinal Cannabis Access Programme (MCap) which allows a consultant to prescribe a cannabis-based treatment for a patient under their care for a small number of conditions, where the patient has not responded to standard treatments.

The conditions include spasticity associated with multiple sclerosis, intractable nausea and vomiting associated with chemotherapy, or severe treatment-resistant epilepsy.

The cannabis-based products included under the MCap include CBD oil drops, oral solutions, and cannabis flower.

The HRB study involved a comprehensive review of the existing evidence from across 30 years on the clinical efficacy and safety of prescribed medicinal cannabis in adult patients only, across medical conditions ranging from cancer, multiple sclerosis and rheumatic diseases, to pain, mental health and neuropsychological conditions.

It focused on evidence related to prescribed medicinal cannabis containing natural or synthetic cannabidiol (CBD) or tetrahydrocannabinol (THC) or their derivatives.

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

But for most other conditions, including anxiety and pain in conditions such as cancer, rheumatic diseases and fibromyalgia, it found no conclusive evidence to confirm the efficacy of prescribed medicinal cannabis.

The review also found that although serious adverse events do not appear to be common, there is some evidence some side-effects such as dizziness, dry mouth, sedation, and headache can occur.

It said more high-quality research was needed in this area.

HRB research officer Dr Kathryn Lambe, lead author of the report, said the study would help inform decision-making in relation to future policy on the use of prescribed medicinal cannabis.