• NHMRC funded study looked at cannabis use in 1500 people with non-cancer chronic pain who had been prescribed opioids and were followed for four years
• 24% of people in the study had used cannabis during the four years of the study
• When cannabis users were asked to rate how effective they felt it was in reducing pain they scored it as moderately effective
• Measures of pain severity, ability to perform daily tasks while in pain and interference of pain in daily life indicated that pain was, in fact, worse in cannabis users compared to non-users. This was the same for people with neuropathic pain or other types of chronic pain.
• The study did not examine types or quality of cannabis used, or directly compare it to placebo in a randomised controlled trial setting.

There is a great deal of interest in the MS community regarding the role that medicinal cannabis may play in helping to manage some of the symptoms of MS. Many people report that cannabis has helped them to manage pain and other symptoms.

However, while clinical trials have shown that cannabis-based medications can be effective in reducing the spasticity that some people with MS experience, the results of clinical trials for pain management have been inconclusive so far.

This study, funded by the National Health and Medical Research Council (NHMRC) and published in the journal Lancet Public Health – you can access the full open-access article here – aimed to examine whether cannabis use was effective in relieving pain in people who had been prescribed opioids for non-cancer chronic pain and whether it was associated with decreased use of opioid medications.

Just over 1500 people were enrolled in the study between 2012 and 2014 and were followed for four years. They completed questionnaires about their use of cannabis, pain intensity, interference of pain in daily life and ability to cope with pain, reasons for cannabis use and also measures of anxiety and depression.

The results showed that people who reported using cannabis for pain either occasionally or frequently rated it as moderately effective in dealing with pain (on average 6.5 on a 10 point scale, where 10 was ‘complete relief’). However, their ratings for pain severity, pain interference (interference of pain in daily life) and pain self-efficacy (confidence to perform tasks while in pain) were all worse than those who did not use cannabis. In addition, they also had higher levels of anxiety.

The researchers used statistical techniques to directly examine any time association between past cannabis use and current pain severity and found that current pain severity was increased in past frequent cannabis users. This helps to rule out the suggestion of ‘reverse causality’ that could indicate that people with worse pain are more likely to use cannabis.  The researchers also did not detect any reduction in opioid medication use in those who previously reported using cannabis.

The researchers did also examine the results for people who specifically reported neuropathic pain (burning or tingling pain associated with nerve damage) but again did not find any effect of cannabis on pain severity in this sub-group.

The mismatch between people’s perception of the efficacy of cannabis in pain management and its lack of efficacy in actually reducing pain scores is an interesting outcome in this study. It suggests that cannabis use may be changing people’s perception of pain by other means. For example, improved sleep, relaxation and other behavioural interventions which are all known to have positive effects in helping people manage pain.

Importantly, this study only asked whether people were cannabis users or not and did not examine the types or composition of the cannabis medications used. This really serves to highlight the great need for robust randomised controlled trials of quality assured cannabis-based medications for the treatment of pain.

Using quality-controlled medicinal cannabis products with known doses of the different active chemical components of cannabis and comparing these products to placebo (dummy medication) will help to answer the question of whether medicinal cannabis can be helpful in treating specific pain conditions or not.

• For more a detailed review of what we currently know about medicinal cannabis in MS and access in Australia read our feature article here
• More information on the use of medicinal cannabis for MS is also available on the TGA website here