HRB: Evidence to support medicinal cannabis use for most conditions is 'inconsistent at best'

Varieties of medicinal cannabis including oils and flowers.

A REVIEW OF research conducted into the use of medicinal cannabis has found that evidence to support the use of the drug in most cases is “inconsistent at best”.

The review of a number of systematic reports into the drug’s use to treat illnesses such as cancer, HIV and aids, Parkinson’s disease and other conditions such as anxiety, said that there was no conclusive evidence to confirm the efficacy of the drug medicinally.

The Health Research Board (HRB) said that many reports noted that the use of cannabis had “no significance” on the pain felt by patients, compared to others using traditional treatments or placebos and that results vary widely in each category.

However, the review also found that there was evidence to support the use of medicinal cannabis for certain symptoms and conditions, such as nausea and vomiting in cancer patients and spasticity in those with multiple sclerosis.

In September last year, the Chief Medical Officer Breda Smyth told the Citizens’ Assembly on Drugs that the use of the drug, illegally, was “of great concern” to the HSE as a result of a spike in the number of people with cannabis-use disorders.

However, it was announced in October that the first medical cannabis production factory on island of Ireland would open at a former fireworks plant in Belfast. Taoiseach Leo Varadkar had previously voiced his support for this measure to The Journal in 2019.

There are also countless examples of medicinal cannabis or cannabinoids (such as CBD or THC) being used to assist those who are ill, including Roderick Campbell whose 2017 column in The Journal detailed how the drug made his father “relax, sleep, laugh, and breathe a bit easier” when living with pulmonary fibrosis.

Most of the research reviewed by the Health Research Board (HRB) noted, however, that there was mixed, low or very low certainty that medicinal cannabis was any better or worse as a treatment compared to traditional medicines.

The review also noted that the research, overall, found there was “low- to very low-certainty evidence” of a significant improvement to perceived pain when a patient used cannabis, compared with placebo groups.

Currently, prescribed medicinal cannabis for certain conditions is approved in Ireland. This includes nausea and vomiting in cancer and spasticity in multiple sclerosis.

The HRB review found, and noted, that there was evidence in the research that supports the use of medicinal cannabis for these conditions.

Dr Kathryn Lambe, lead author of the report, said while the review does indicate there is evidence to support the continued use of medicinal cannabis in the current legal conditions, in most other outcomes “the findings were inconsistent at best”.

Medicinal cannabis’ use for conditions in older adults – such as dementia, Alzheimer’s and Parkinson’s disease – were found to cause secondary outcomes such as agitation or aggression, changes in quality of life, functional outcomes, dementia severity or nutritional outcomes, and carer burden.

Adverse events included drowsiness or sedation, sleeplessness or adverse effects on sleep, changes to the nervous system, and gastrointestinal effects. Sedation was noted to be more common with cannabinoid interventions than with placebo.

The study was conducted to inform a Department of Health review of the current Medicinal Cannabis Access Programme (MCAP). While it did find evidence to support its current use, there’s little evidence which would indicate that the MCAP would be expanded as a result of this review.

There was 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 there was very little evidence to support its use to treat other conditions.

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