Knowledge Gaps in Placebo Research: With Special Reference to Neurobiology.

This article addresses different ways to identify knowledge gaps in placebo research. Following a short description of the history of placebo research and our contributions, we describe the creation of the Journal of Interdisciplinary Placebo Studies (JIPS) literature database and compare its content (on a meta-level) with two other approaches to survey the current state of the art of placebo research: a bibliometric analysis of a (limited) selection of placebo papers, and the analysis of the content of all abstracts submitted to a 2017 placebo conference. We summarize this discussion with a critical assessment of these approaches and a perspective of future approaches in such placebo "meta"-analyses.