Systematic review and meta-analyses of studies analysing instructions to authors from 1987 to 2017.

To gain insight into changes of scholarly journals’ recommendations, we conducted a systematic review of studies that analysed journals’ Instructions to Authors (ItAs). We summarised results of 153 studies, and meta-analysed how often ItAs addressed: 1) authorship, 2) conflicts of interest, 3) data sharing, 4) ethics approval, 5) funding disclosure, and 6) International Committee of Medical Journal Editors’ Uniform Requirements for Manuscripts. For each topic we found large between-study heterogeneity. Here, we show six factors that explained most of that heterogeneity: 1) time (addressing of topics generally increased over time), 2) country (large differences found between countries), 3) database indexation (large differences found between databases), 4) impact factor (topics were more often addressed in highest than in lowest impact factor journals), 5) discipline (topics were more often addressed in Health Sciences than in other disciplines), and 6) sub-discipline (topics were more often addressed in general than in sub-disciplinary journals). Publishers’ policies have the capability to increase transparency in scholarly literature. Malicki and colleagues carried out a systematic review of over 150 studies that have examined scholarly journals’ recommendations. They find that requirements in terms of authorship, conflict of interests, data sharing, funding disclosure or ethics approval declaration vary greatly over time, among journals and across disciplines.