[Evidence of the efficacy and safety of cannabis medicines for chronic pain management : A methodological minefield].

Recent systematic reviews (SRs) came to divergent conclusions on the efficacy and safety of medical marijuana and cannabis-based medicines for chronic pain management. This paper gives an overview and critical appraisal of the methods of recent SRs of randomized controlled trials (RCTs) with cannabis medicines for chronic pain.Selective search of the literature, incorrect data analyses and presentation in favor of cannabis medicines can be detected in both RCTs and SRs. The more detailed the search of literature (e.g. inclusion of so-called grey literature) and the higher the criteria of the inclusion of studies (such as study duration) and of the clinical relevance of the study findings, the more disappointing are the conclusions of SRs on the efficacy and safety of cannabis medicines. There is moderate quality evidence of a moderate relief of neuropathic pain. Cannabis medicines can be regarded to be third-line therapy for chronic neuropathic pain. There are signals of a lack of efficacy for all other chronic pain syndromes.New high-quality RCTs and approaches, such as network meta-analyses combining different treatments and controlled and observational including additional outcomes than pain relief, are necessary to better define the importance of cannabis medicines for chronic pain management.