When submitting a manuscript to a journal, authors are always asked to disclose potential conflicts of interest. A conflict of interest is any activity or role of an author that might cause bias in the research conducted in the paper. Ideally conflicts of interest should be avoided, but in reality this is not always possible; for example, an author might be a consultant for a drug company because he or she is an expert in the field. The purpose of declaring conflicts of interest in scientific papers is to provide transparency in reporting science to the public, and to give readers an opportunity to judge the value of the publication.
Conflicts of interest can be financial or non-financial. All journals require disclosure of financial relationships (funding, employment, stocks, consultant fees, lecturing fees, etc), while some journals also require disclosure of non-financial relationships (unpaid advisory role, membership, etc, sometimes even political or personal beliefs). Many medical journals use the International Committee of Medical Journal Editors (ICMJE) Form for Disclosure of Conflicts of Interest, which does include non-financial relationships. Nature journals only started requesting authors to disclose competing non-financial interests this year. Authors should always check journal guidelines about what to include. Only relationships relevant to the study in the manuscript need to be declared. There is no definite cut-off as to how relevant or how much money is involved when a conflict of interest has to be reported. The authors will need to make their own judgment, but if it is something that a reader might perceive as can affect the objectivity of the author, it should be disclosed.
If a conflict of interest is not disclosed in a published paper but later found out by a reader and reported to the journal, the journal usually will ask the authors to clarify whether such a claim is true and may ask the authors’ institution to investigate if the research is still credible. Failure to disclose conflicts of interest generally will not lead to retraction of the paper by the journal, but the authors will need to update their disclosure and the journal would publish a correction. However, retractions may happen if journals find that the authors have omitted major conflicts of interest that are likely to influence the study.
Of course, authors are not the only ones who need to disclose conflicts of interest during the publication process. Reviewers and editors are also required to disclose any potential conflicts of interest to the editorial board when handling a paper.