The association between funding by commercial interests and study outcome in randomized controlled drug trials

Background. Previous studies limited to specific drugs or journal types have shown an association between the source of funding of research and the published results. Objective. The aim of the present study was to determine the association between source of support of research and published outcomes of randomized controlled drug trials in general interest medical journals. Methods. Randomized controlled drug trials (n = 314) published in five general interest medical journals over a 2-year period were reviewed. Study outcome was classified as positive or negative. Support was classified as pharmaceutical industry or non-industry. Association between source of support and outcome was tested with the chi-squared statistic. Results. Positive findings were found in 77% of studies, negative findings in 20% and an uncertain outcome in 3%. Support from commercial sources was found in 68% of trials. Negative findings were found in 13% of industry-supported studies and in 35% of non-industry-supported studies (chi-squared = 18.36, P < 0.0001, odds ratio = 3.54, 95% confidence interval 1.90-6.62). Conclusions. An association was found between the source of study support and the published outcome. Though the reason for this association cannot be determined from the data collected, future studies may clarify the importance of this finding for readers concerned with the relationship of funding bodies to the publication of research outcomes.