Do Conflict of Interests Disclosures Work? Evidence from Citations in Medical Journals

Financial ties between drug companies and medical researchers are thought to bias studies published in medical journals. To enable readers to account for such bias, most medical journals require authors to disclose potential conflicts of interest. We examine whether disclosure reduces article citations, indicating a discount. A challenge to estimating this effect is selection as drug companies may seek out higher quality authors. Our analysis confirms this positive association. Including observable controls for article and author quality attenuates but does not eliminate this relation. We perform three tests. First, we show that the positive association is weaker for review articles, which are more susceptible to bias. Second, we examine article recommendations to family physicians among articles that are a priori more homogenous in quality. We find a significantly negative association between disclosure and expert recommendations, consistent with discounting. Third, we conduct an analysis within author and article, exploiting journal policy changes that result in conflict disclosure by an author. We examine the effect of this disclosure on citations to a previously published article by the same author. This analysis reveals a negative citation effect. Overall, our evidence is consistent with the notion that other researchers discount articles with disclosed conflicts.