Recently, the debate on the legalization of cannabis (Latin for hemp) was once again making waves among political factions. When interest groups advocate for the legalization of cannabis, multiple sclerosis is usually brought up. The potential effects of cannabis on MS are considered an important pro-argument. I do not want to discuss here what I personally think about the legalization of cannabis, or whether it makes sense to criminalize cannabis consumers. However, I do want to briefly outline the effects that MS patients can expect from cannabis (preparations) according to the current state of knowledge – in my view, there is no significant additional need from this perspective.
Cannabis is the most commonly consumed illegal drug – users appreciate its relaxing effect. In addition, a sedative (calming) and antiemetic (suppressing nausea and vomiting) effect of cannabis has been described, which modern medicine currently makes use of: cannabis preparations are used in cancer and AIDS patients to combat nausea and loss of appetite, and here they have an undisputedly helpful effect.
MS patients also occasionally report the positive effect of a “joint” on their general well-being – and, if present, on a spastic increase in tone/spastic paralysis. Based on this observation, studies with cannabis in MS have been conducted since the 80s. These studies typically use an oral formulation of the cannabinoid tetrahydrocannabinol (THC), which is a main component of the compressed, resin-rich parts of the hemp plant and is primarily responsible for the relaxing, sedative, and antiemetic effects of a “joint”.
One of the largest and most famous studies is the so-called CAMS study, which was published in 2003 in the renowned science magazine “The Lancet” by Prof. John Zajicek and colleagues and examined the effect of cannabis in over 600 patients in Great Britain. The quintessence of the study was that no significant difference could be achieved between the patients in the cannabis group and those in the placebo group. The study was therefore negative. Nevertheless, the authors concluded that individual patients had benefited and promoted further scientific investigation of the topic “MS therapy with cannabis”, also against the background of a neuroprotective effect suspected from animal experiments.
Therefore, the so-called CUPID study was conducted – also in Great Britain under the direction of J. Zajicek – which examined the effect of Dronabinol (=THC) on chronic progressive multiple sclerosis in almost 500 patients with this form of disease. The results of the study were published in Lancet Neurology in 2013. To make it short – the study showed no therapeutic effect of cannabis on chronic progressive MS. Thus, the hope of a neuroprotective effect of cannabis could not be confirmed by this study.
In this context, I find noteworthy a recently published paper (Romero, Neuroimage 2015), which demonstrated harmful effects of regular cannabis use in MS patients using MRI and reported an increase in cognitive disorders and changes in gray matter. So despite all the euphoria of some patients, one cannot safely rule out harmful effects of cannabis.
What remains is a possible antispastic effect of cannabis, which formed the basis for the development of Sativex® (Nabiximols). This cannabis preparation is now approved for the treatment of spasticity in MS based on positive studies and is available on prescription (narcotic prescription). Sativex is a combination preparation of THC and Cannabidiol (CBD), a cannabinoid that partially antagonizes the psychoactive effects of THC. Thus, Sativex® is much better tolerated than previous cannabis preparations based on THC with comparable antispastic potency.
We observe some good therapeutic effects with Sativex in the treatment of spasticity in MS patients, but sometimes we also see no significant effects at all. Therefore, I currently see cannabis preparations as a welcome addition to the antispastic therapy in MS. However, they are certainly not a breakthrough, also considering the already available antispastic therapies.
Therefore, I think that the effect of cannabis on multiple sclerosis has been quite well studied and there is no extremely high need for legalization according to the current state of knowledge (from the perspective of the MS therapist). When it comes to this question, multiple sclerosis is not a really good argument.
