Occupational and environmental health studies with industry funding are more than four times as likely to report negative results, an analysis of hundreds of scientific papers has found.

Researchers from the University of Illinois at Chicago School of Public Health also identified a ‘dose-response’ effect, meaning the greater the industry backing the greater the likelihood the study would find nothing to worry about.

Lee Friedman and David Friedman analysed 373 original research articles published in 2012 in 17 peer-reviewed occupational and environmental health journals. They found “a clear relationship between negative results in studies evaluating adverse health outcomes in humans and financial COI [conflicts of interest] arising from relationships with organisations involved in the processing, use, or disposal of industrial and commercial products.”

These studies were 4.31 times as likely to report negative results. Where the backing came from the military, negative results were more than nine times as common. The authors found occupational and environmental health research funded by public agencies didn’t have a bias towards positive results.

The paper, published in the Journal of Occupational and Environmental Medicine, notes: “A publication bias can be caused by multiple factors, including inappropriate study design, biased interpretation or presentation of results, legal obstruction preventing an author from publishing results, and failure to report findings that are found to be damaging to the interests of the funding organisation.

“The findings presented in this analysis show a clear association between financial COI and reported findings, and the direction, magnitude, and observed ‘dose-response’ effect of the relationship is consistent with the vast majority of similar studies in other scientific fields (eg. pharmacology, biomedicine, and so on), which demonstrates the need for further research in the field of environmental and occupational health to determine whether this observed association is a product of an underlying publication bias, in particular the omission of studies showing ‘positive’ findings within the public forum.”

• Lee Friedman and Michael Friedman. Financial Conflicts of Interest and Study Results in Environmental and Occupational Health Research, Journal of Occupational and Environmental Medicine, volume 58, issue 3, pages 238–247, March 2016 [abstract].