Does the type of competing interest statement affect readers' perceptions of the credibility of research? Randomised trial

Financial relationships among industry and academic institutions are diverse and common.1 These interests can influence authors' conclusions2 and readers' perceptions of published studies.3 We report the effects on reader perceptions of different statements of competing interests for two manuscripts. We used computer generated random numbers from the British Medical Association's membership database (to select 900 BMJ readers). We randomised 450 to be sent a paper about the use of problem lists in letters between hospital doctors and general practitioners4 (problem lists paper) and 450 to be sent a paper indicating that the impact of pain from herpes zoster on patients' daily functioning may be substantial (herpes paper).5 We previously reported a study using the herpes paper,3 and we have incorporated the results from that study in this paper. For each of the papers, 150 readers received the paper with no competing interests declared, 150 with a financial statement, and 150 with a statement that the author was a recipient of funding for studentships and research grants. The competing interest statements for each group were as follows. For both papers, when the type of competing interest was “none,” the phrasing of …