Are cannabinoids more effective than placebo in decreasing MS-related bladder dysfunction?

Bladder dysfunction is one of the most common symptoms in people with multiple sclerosis (MS). The estimated prevalence of bladder difficulties in MS has varied, depending on the populations studied. Estimates of between 52 and 97% have been cited (Hawker and Frohman, 2001). Bladder dysfunction may affect quality of life and some people with MS use cannabis to alleviate urinary and other MS symptoms (Brady et al, 2004). It has been reported that cannabinoids and cannabinoid agonists decrease motility in normal and inflamed bladders (Merriam et al, 2008). This mini-review aims to provide the summary of evidence of a single question and its outcomes with limited scope as described by Griffiths (2002). The author will analyse new evidence of the use of cannabinoids in bladder management to identify whether cannabinoids are more effective than placebo in decreasing MS-related bladder dysfunction. A systematic literature search was undertaken to identify all studies comparing the effects of cannabinoids with placebo. The MEDLINE and Embase databases were searched. Two randomized controlled trials were identified. Results showed that both studies compared the effectiveness of cannabinoids with placebo in decreasing MS-related bladder dysfunction; however, they used different protocols, different cannabinoids and a different number of subjects. One of the studies was underpowered and showed no statistical significance in the reduction of daily incontinence episodes. The other study was a sub-study that assessed secondary outcomes. The studies showed a number of limitations and, considering that the main outcome for both studies was the number of incontinence episodes, they showed some evidence that cannabinoids provided some benefit in different symptoms of bladder dysfunction in people with MS. Further research in the effectiveness of cannabinoids on MS-related bladder dysfunction is recommended to answer this question. Randomized controlled trials that include all aspects of bladder dysfunction and differentiate between the different types of bladder incontinence will be recommended.