What should a reviewer do if they have a non-financial conflict of interest?

A reviewer is expected to maintain the integrity of the peer review process, and that includes managing any conflicts of interest that may arise. If a reviewer has a non-financial conflict of interest, such as a personal relationship with the author of the manuscript or a professional rivalry, the best course of action would be to inform the editor about the conflict. This allows the editor to determine whether the reviewer should continue with the review or if another reviewer should be assigned. By taking this responsible step, the reviewer helps to ensure that the evaluation of the manuscript remains objective and fair, thereby upholding the standards of academic integrity in the publication process.

The other choices would not align with ethical guidelines in scholarly publishing. Not disclosing a conflict and taking no action could compromise the integrity of the review process, while withdrawing from the review might not address the conflict adequately unless it clearly impacts the reviewer's ability to provide an unbiased assessment.