Medical cannabis is becoming increasingly prescribed for a wide variety of illnesses and health conditions. However, the clinical evidence regarding this category of medications is still relatively lacking, following decades of prohibition and limited access to the drugs. While there is still a lack of clinical evidence, the harnessing of real-world data is largely considered an effective way to generate further insights to improve research and current clinical care. In contribution to this aim, the UK Medical Cannabis Registry was launched by Sapphire Medical Clinic in 2019.
Early this year, an updated analysis of the data collected through this registry was published, offering an insight into the changes in general health-related quality of life in patients prescribed medical cannabis (HRQoL). An important aspect of this research is also associated clinical safety of cannabis-based medical products (CBMPs). This recent analysis looks at these two aspects in more detail.
Medical cannabis is currently available for a number of health conditions and illnesses – though this availability can largely depend on where you are in the world. The medicinal use of cannabis was effectively legalised in the UK at the end of 2018; however, patient access is still largely limited as CBMPs are not yet routinely available through the NHS.
The vast majority of patients in the UK currently access medical cannabis through private clinics. Sapphire Medical Clinics established the UK Medical Cannabis Registry in December 2019 to capture data to progress medical cannabis evidence. The current analysis of the data includes 312 patients in the UK with a mean age of 44.8.
The most common indications represented in this sample were chronic pain of undefined aetiology (32.7%), neuropathic pain (13.8%), and fibromyalgia (9.9%). Notably, these are conditions that commonly have a significant impact on patient quality of life.
Design and Methods of the Study
The UK Medical Cannabis Registry was established to collect pseudonymised outcomes and adverse events of patients prescribed CBMPs. For data collection, patients were asked to complete patient-reported outcome measures (PROMs) and adverse event questionnaires prior to the initiation of medical cannabis and at 1-, 3-, and 6-months follow-ups.
Past cannabis use, alcohol, and tobacco consumption were also recorded at baseline. A novel metric of “cannabis gram years” was devised to calculate the amount of illicit cannabis consumed if a patient had a history of use.
Health-Related Quality of Life (HRQoL)
The primary outcome of this analysis was HRQoL of medical cannabis patients. This outcome has become a key factor in assessing the effects following initiation of therapy.
The PROMs completed by all patients included the Generalised Anxiety Disorder Scale (GAD-7), EQ-5D-5L, and Sleep Quality Scale (SQS). The incidence of adverse events was captured synchronously with the completion of PROMs or during routine clinician follow-up.
Quality of Life scores
The data collected through the UK Medical Cannabis Registry showed an improvement in general HRQoL in the studied patients following initiation of therapy, which was sustained at six months. These findings build on previous analysis at 3 months.
The results collected show statistically significant improvements at each of the follow-up dates compared with baseline scores according to reported GAD-7, EQ-5D Index value, EQ Visual Analog Scale, and SQS outcomes. Furthermore, there were also statistically significant improvements as determined by EQ-5D-5L Self-Care subscale at 1 month, EQ-5D-5L Mobility subscale at 1 and 3 months, and the EQ-5D-5L Usual Activities, EQ-5D-5L Pain and Discomfort, and EQ-5D-5L Anxiety and Depression subscales at the 1-, 3-, and 6-month follow-ups.
Interestingly, there was a significantly larger EQ-5D-5L pain and discomfort score for the cannabis-naïve group analysed at the 1-month and 1-month follow-ups, while there was a significantly larger EQ-5D-5L Index score at the 3-month follow-up and EQ-VAS score at the 1-month follow-ups to those who reported consuming cannabis at baseline.
This contrasts with previous data from the UK Medical Cannabis Registry, which showed greater improvements in pain-specific PROMs in those who were previously naive to cannabis prescribed a specific group of oil-based CBMPs. The researchers suggest that this discrepancy could “represent the breadth of CBMPs studied within the present analysis, with previous cannabis consumers benefitting from more rapid titration of dose and initiation of flower and oils.
As previously identified in an analysis of the registry to determine efficacy for generalised anxiety disorder, medical cannabis therapy was associated with modest changes in anxiety scores using the EQ-5D-5l anxiety and depression subscale and GAD-7. In this sample, there were greater changes in GAD-7 scores at 3- and 6-month time periods.
In total, 94 adverse events were reported – an incidence of 30.1%. The most commonly reported adverse events were nausea (n=12, 3.8%), dry mouth (n=10, 3.2%), dizziness (n=7, 2.2%), and somnolence (n=7, 2.2%). Adverse events were most commonly reported to be mild (n=46, 14.7%) in severity, while only 1 event, being insomnia, was deemed as disabling. The most-reported “other” adverse events were diarrhoea (n=3, 1.0%), depression (n=2, 0.6%), and anxiety (n=2, 0.6%).
Cannabis-naïve patients were more likely to experience adverse events, with 47 (15.1%) of this group reporting adverse events, compared with 26 (8.3%) of patients who were consuming cannabis at baseline, and 18 (5.8%) of prior cannabis users.
The researchers conclude that these findings suggest medical cannabis was “associated with an acceptable safety profile and improved HRQoL outcomes across a broad spectrum of chronic conditions at 1-, 3-, and 6-month follow-ups compared to baseline.”
This study identified an increased adverse event incidence in comparison to a previous interim analysis of the UKMCR. This may be representative of increased length of prescribing allowing for greater accumulation over time, highlighting the importance of ongoing pharmacovigilance to better inform clinicians and patients regarding the potential risks of medical cannabis.