One of the strengths of this study is that we are addressing a fundamental question over so-called routine clinical research procedures. We tried to provide a more comprehensive understanding of any association of placebo disclosure in PILs with methodological issues in clinical research, i.e. blinding, and the effect size. Previous studies have usually focused on ethics , readability , or comprehensiveness , but few studies explored association of pre-trial information on placebo with blinding and trial outcomes, which definitely requires further investigations from a different point of view. Another strength would be that it encompasses qualitative and quantitative research designs. Collected PILs were subject to systematic qualitative content analysis method . Then, numerical analyses such as calculating BI and effect size were conducted in conjunction with the results from content analysis. Such integrated method can help science achieve better understanding of its discoveries .