Conflicts of interest and outcomes of clinical trials of antidepressants: An 18-year retrospective study

Abstract

Pharmaceutical sponsorship, funding sources, and investigators' conflicts of interest may be potential influencers in the conduct and results of clinical trials, as well as in the promotion of psychiatric drug therapies. We report the results of an audit of randomized controlled trials (RCTs) of antidepressants conducted from 2000 to 2017. We searched the Web of Science databases with a comprehensive search strategy to identify phase 2 and 3 RCTs. Out of the 1085 articles initially located, a total of 291 RCTs were identified and included in the final analyses. A higher percentage of RCTs conducted by employees of pharmaceutical companies reported favorable results than those with academic or governmental funding (76.90% vs. 60.60%); however, this association was not significant (Χ 2 = 2.47, P = 0.18). The data were further analyzed using bivariate and cluster analytical approaches, and the nonsignificant association persisted in both cases. However, analyses of industry-funded placebo-controlled trials (a subgroup of the 291 RCTs) revealed a higher proportion of results that were reported as significant compared to their counterparts with other funding sources (67% vs. 33%). This association was statistically significant (Χ 2 = 9.56, P = 0.002), indicating that there is evidence in support of conflicts of interest as a potential bias in the outcomes of RCTs conducted for antidepressants.