Sir, We were interested to read the report by Blake et al.  in your journal.
Between 1998 and 2002 we surveyed a sample of 2969 people with various chronic diseases in the UK, with the aim of investigating the reasons for the medicinal use of cannabis . In that survey, arthritis was reported to be among the five most common reasons for the medicinal use of cannabis, and we reported that of those who had reported using cannabis for the relief of their symptoms, 21% did so specifically for the relief of the symptoms of arthritis. The publication of your recent article prompted us into a review of the data collected, in order to determine what proportion of those respondents suffered from rheumatoid arthritis, and how their symptoms responded to the use of cannabis.
Of the 2969 respondents to the survey, 784 (26%) stated that they had ‘arthritis’. Of these, 247 patients indicated that they suffered from rheumatoid or osteoarthritis (the remainder did not specify). A total of 155 respondents stated that they continued to use illicit cannabis for the purpose of symptom relief. Around 111 of them (46%) had rheumatoid arthritis. Respondents were asked to indicate how their condition was affected by the use of cannabis. Of those patients with arthritis who responded to this question, 172 stated that it made them ‘much better’, 53 stated that it made them ‘a little better’ and five stated that it ‘made no difference’. None of the patients indicated that their arthritis was worsened by the use of cannabis.
Of those respondents who used illicit cannabis for rheumatoid arthritis, 100% indicated that they found it made them either ‘much better’ (72%) or ‘a little better’ (28%). We can conclude from this review of the original data, that the illicit use of cannabis by patients with rheumatoid arthritis is widespread, and that there is anecdotal evidence of effectiveness.
At that time, the authors pointed to the need for clinical studies of quality-controlled cannabis preparations to explore these conclusions in a more scientific and systematic way. We now note that the results of a formal randomized and controlled clinical study of the use of a medicinal grade of a cannabis extract validates this anecdotal evidence of the benefit of cannabinoids in the relief of the symptoms of rheumatoid arthritis. It will be of considerable interest to observe whether other conditions for which only anecdotal evidence currently exists may be validated in a similar manner in clinical trials of standardized cannabis preparations.
The authors have declared the conflicts of interest as G.G. is the Executive Chairman and founder of GW Pharmaceuticals. M.W. has participated in and received honoraria for CME articles from Bayer, Valeant and Solvay, and has received grants from GW and Valeant. S.W. is a full-time employee of GW.
1GW Pharmaceuticals pic, Salisbury, Wiltshire, UK, 2McGill University, Departments of Anaesthesia and Family Medicine, Montreal, Quebac, Canada