Peer reviewers altered their recommendation based on whether they were cited or wanted to be cited. A matched study of open peer review at four journals.

Peer reviewers judge the validity and quality of new research. These judgements would ideally be impartial, but some reviewers may give a more favourable review if they are cited in the article because the authors have recognised their work and because citations are a valuable academic currency. Reviewers sometimes request self-citations to their own work, which may be justified as reviewers should be relevant experts. However, some self-citation requests may be unethical, with reviewers exploiting the authors' need to publish. We examined whether citations to a reviewer and self-citations influenced their peer review. We used a matched design at four journals that use open peer review and make all article versions available. Our sample included more than 37,000 peer reviews, with 13% where the reviewer was cited in the article and 6% where the reviewer included a self-citation to their work in their review. Reviewers who were cited were more likely to approve the article, with an odds ratio of 1.61 compared with reviewers who were not cited (adjusted 99.4% CI: 1.16 to 2.23). Reviewers who suggested a self-citation were much less likely to approve the article, with an odds ratio of 0.15 compared with reviewers with no self-citations (adjusted 99.4% CI: 0.08 to 0.30). Reviewers who requested and received a citation were much more likely to approve the article compared to reviewers whose request was disregarded (odds ratio of 3.5, 95% CI: 2.0 to 6.1). Some reviewers' recommendations are dependent on whether they are cited or want to be cited. Self-citation requests can turn peer review into a transaction rather than an objective critique of the article.