This review attempted to answer the question, what is the highest level of evidence available for the efficacy of pharmaceutical and nonpharmaceutical interventions for patients with MUS, and where have these studies been carried out?
The strength of evidence of the effectiveness of any intervention was assessed from a hierarchy based on study design. Search for evidence was confined to level I (systematic review) and level II (randomized controlled trial [RCT]) evidence.
Adapting a hierarchical approach by examining the highest level of evidence was the aim. If evidence was present at level I, the review did not proceed further to obtain level II evidence. The aim was to identify the gaps and then to report any recent advances made since the last systematic review. Therefore, level II evidence (individual RCTs, published since last available systematic review) were also examined.