Does cannabis help pain management?

November 27, 2023 news

This week's paper is on a topic that we haven't covered before; cannabis. Hailing from a mostly Canadian team, the study was a systematic review and meta-analysis of randomised controlled trials. That's a good level of evidence. Published in March 2021, the study, called "Medical cannabis or cannabinoids for chronic non-cancer and cancer-related pain: a systematic review and meta-analysis of randomised clinical trials," was authored by Wang et al.

There were conflicts of interest to note. Three of the 21 authors had cannabis industry conflicts, but these did not include the first or last named authors (the most influential authors). Additionally, 21 out of 32 trials were funded by industry. Had the claims been strident, the conflicts would have been of concern, but the claims were relatively modest.

Cannabis (also called marijuana) refers to the dried leaves, flowers, stems and seeds from the Cannabis sativa or cannabis indica plant. Extracted ingredients can be active or inactive. You may have heard of CBD and THC, as the main examples(CBD is non-addictive, THC is the 'primary psychoactive' element. Approximately one-third of individuals aged 16-59 in England and Wales have tried cannabis, making it one of the most commonly used recreational drugs.

The Wang et al. study used the term "medical cannabis" to encompass various cannabis-based medicines designed to alleviate symptoms. A systematic review involves a comprehensive examination of literature on a specific topic, pooling evidence to discern overall trends. The criteria for the selected studies included being randomised controlled trials, enrolling a minimum of 20 chronic pain patients with pain lasting at least 3 months.

The systematic review identified 32 relevant trials, involving 5,174 adults, with 28 trials suitable for meta-analysis. Medical cannabis was administered orally in 30 trials and topically in 2, focusing mainly on non-cancer pain (28 trials) and pain in cancer patients (4 trials). Follow-up durations ranged from 1 to 5.5 months.

Outcome measures included pain intensity, physical, emotional, role, and social functioning, as well as sleep quality. Adverse events such as cognitive impairment, vomiting, drowsiness, impaired attention, diarrhoea, and nausea were also assessed.

The results revealed modest benefits of non-inhaled medical cannabis, including a probable small increase in pain relief, a very small improvement in physical functioning, and a small improvement in sleep quality. Adverse effects, such as cognitive impairment and dizziness, were identified with varying levels of certainty.

In conclusion, the study provided a comprehensive exploration of medical cannabis for chronic pain, addressing the strengths and limitations of the research. Its findings prompted the BMJ to issue a "Rapid recommendation," that medical cannabis should be considered for chronic pain where standard care has not helped thus far. The recommendation remains open to adjustment pending further research, highlighting the evolving nature of the evidence.