More than one-third of Cochrane reviews had gift authors, whereas ghost authorship was rare

Objectives: To determine the prevalence of gift and ghost authors in Cochrane reviews and to investigate possible predictors of gift authorship. Study Design and Setting: An Internet-based survey was sent in April 2019 to 1,226 first authors of Cochrane reviews published between October 2016 and December 2018. Three reminders were sent. Responses were anonymized before data extraction. Results: A total of 666 of 1,226 (54%) first authors completed the survey. The prevalence of gift authors was 41% and 2% reported ghost authorships. Of the first authors, 15% were not aware of the authorship criteria from the International Committee of Medical Journal Editors. In a multivariable analysis, factors associated with the existence of gift authorship were: first author was not aware of the International Committee of Medical Journal Editors authorship guidelines (odds ratio (OR) 2.08, 95% confidence interval (CI) 1.23–3.51, P = 0.006), increasing number of authors (P < 0.001), and first author had offered an inappropriate authorship previously in their academic career (OR 1.96, 95% CI 1.23–3.13, P = 0.005). Conclusion: A substantial proportion of Cochrane reviews showed evidence of gift authorship, whereas ghost authorship was less prevalent. Thus, there is a need to increase awareness of this persistent issue in Cochrane reviews.