Cannabis and Chronic Pain
by John Finch
The journal Pain recently published an important study on the use of cannabis, and medicines based on cannabis (cannabinoids), for chronic pain conditions (chronic pain in cancer patients was specifically excluded). Researchers were from institutes in Sydney, Brisbane and London specialising in substance abuse and addiction. The study involved reviewing published data from trials and clinical reports where cannabinoids had been used in patients with neuropathy, fibromyalgia, rheumatoid arthritis, multiple sclerosis, visceral pain or undefined pain. The researchers looked at the results for 30% or 50% reduction in pain and the proportion of patients who obtained that benefit. In summary 29% of patients receiving cannabinoids reported a 30% reduction in pain compared with 26% receiving placebo. Statistical analysis showed that this difference was real, but 24 patients have to be treated for there to be one who gets this benefit. When 50% reduction in pain was looked at there was no significant difference between patients receiving cannabinoids and placebo. Furthermore, there were no measurable benefits in emotional or physical functioning. Side effects included dizziness, difficulty in concentration or comprehension, confusion or disorientation. They were commonly observed and only 6 patients needed to be treated for there to be one who experienced side effects. The studies reviewed by these researchers collectively involved nearly 10,000 patients. They found that 24 patients need to be treated for there to be one experiencing a benefit and that for every 6 treated there is likely to be one with harmful side effects. And so, they conclude that it is unlikely that cannabinoids are an effective medicine for chronic non-cancer pain. The researchers point out that many of the studies were very small, many were with patients who were already on other pain medicines, some were short term studies despite dealing with a chronic condition and finally, chronic pain itself is highly complex condition. They state that long term large-scale well-designed trials will be needed to provide definitive evidence on any benefit for cannabinoids in chronic pain.
Letter to The Times
A recent letter to The Times signed by more than 150 pain medicine consults including Pain Concern’s medical advisor raised concerns about a recent decision by the UK government to allow specialist pain doctors to prescribe cannabinoids for chronic pain, describing the decision as premature.
Pain Concern’s Medical Advisor, Dr Cathy Price commented that she signed it as she fully shared the concerns of virtually all pain clinic consultants in the UK:
Firstly, the people who benefit the most are not clear with a very small number who benefit substantially compared to the number who are harmed by cannabis. A very recent systematic review published in Pain this month provided scientific evidence to justify our concerns. Secondly, the number of people with chronic pain is very large and potentially there could be many people wanting cannabis but likely to benefit very little. This could potentially have denied other more effective treatment to patients.
While other doctors have written to The Times disagreeing with the letter it remains true that there is near unanimity among pain consultants that there is little evidence to support the use of cannabinoids in chronic pain.
The Faculty of Pain Medicine has issued a position statement broadly supportive of this position pointing out the lack of evidence of benefit and clear evidence of potential harm from cannabis. The pain profession seems united in wanting more evidence but for the moment remaining doubtful that cannabinoids have a role in the treatment of non-cancer chronic pain