The New York Review of Books has a extensive review written by Richard Horton of the book Science in the Private Interest: Has the Lure of Profits Corrupted Biomedical Research? by Sheldon Krimsky. The review has an extensive bibliography, and cites some good work about problems with the quality and conclusions of corporate sponsored research.
For example, Stelfox showed in a 1998 NEJM article [Medline] that conclusions drawn by authors about calcium channel blockers were strongly associated with the funding support the authors received. Bero showed in a 1992 NEJM article [Medline] that journal supplements for symposiums were more likely to have misleading titles, more likely to use brand names, and less likely to have peer review if the symposium was sponsored by a single company. Rochon showed in a 1994 Arch Intern Med article [Medline] that manufacturer supported trials of nonsteroidal anti-inflammatory drugs were never critical and showed either comparability (71% of the time) or superiority (29% of the time) to the comparison drug. These trials also claimed less toxicity relative to the comparison drug in 86% of the publications.
Not cited in the review is the substantial evidence that association with tobacco interests has a large and quantifiable impact on the findings of a study. An article by Barnes published in 1998 in JAMA [Medline] that showed articles on passive smoking written by authors affiliated with the tobacco industry were far more likely to conclude that passive smoking was not harmful. Another article by Barnes, published in 1997 in Tob Control [Medline], showed, interestingly enough, that tobacco industry affiliation was not associated with lower quality, but that symposium articles in general had poorer quality scores than peer-reviewed articles. A review of studies on the economic effects of laws restricting smoking by Scollo 2003 BMJ Tob Control [Medline] showed that tobacco affiliations were associated with greater use of subjective outcomes, a lower rate of peer review, and a greater tendency to report negative economic impacts.
An article by Angell in NEJM [Medline] noted the special problems that conflict of interest poses for the authors of editorials, which heavily lean on subjective assessments of evidence.
A1986 review by Davidson in 1986 in J Gen Intern Med [Medline] showed that source of funding was indeed related to the conclusion drawn by the author as does Kjaergard in a 2002 BMJ article [Medline]. Friedberg notes in a 1999 JAMA article [Medline] that funding source does not lead to unwarranted positive conclusions in economic analyses of new drugs but that authors with industry support as less likely to draw unfavorable conclusions about the drug being studied. A systematic review by Lexchin, in a 2003 BMJ article [Medline] shows problems with industry sponsored research. Possible explanations are publication bias or the use of an ineffective comparator drug. On the other hand, Clifford noted in a 2002 article in BMC Health Services Research article [Medline] that a recent sample of randomized trials in five high impact journals showed no association between funding source and either quality or the conclusions drawn.
All of us will admit that conflicts of interest can influence other people's judgments, but as Boyd points out in a 2003 article in Acad Med [Medline], we as individuals stubbornly cling to the belief that we can rise above the potential conflict. This is not unlike the belief mentioned by Katz in 2003 in the American Journal of Bioethics [Medline] that physicians are unaffected by the small gifts that drug companies often use as a marketing tools.
Is there an explicit assurance from the author that the industry support still allowed the author to independently assess the data and to publish the results without first getting approval from the sponsor? A reasonable review period by the sponsor is acceptable as long the final decision to publish rests with the author and not the sponsor. A 2001 revision to the statement on publication ethics from the International Committee of Medical Journal Editors highlights how important this assurance is.
Another problem is that authors rarely disclose possible conflicts. Hussain in the 2001 BMJ [Medline] calculated the rate of disclosure at 1.4% (52 out of 3,642). Not all authors have a conflict, of course, but the very low rate here makes me suspicious that most authors with a conflict fail to report it.
The general conclusion I would draw is that a conflict of interest is not an automatic disqualification, but that you should instead demand a higher level of evidence. Is the data laid out in such a way to allow you to make a complete assessment of the quality of the author's conclusions?
Keep in mind that sometimes the conflict is not in the author of the study, but in the reader of the study. Lerner in a 2002 Cmaj article [Medline], highlights the controversy over breast self exam. Because the use of this exam is empowering, because it promotes self care, and because of a general belief in individual testimonials, many readers have reacted angrily to reports that use of a breast self-exam has no detectable impact on mortality. I've already commented on David Sackett's editorial, "The arrogance of preventive medicine" but there is also a very informative review article by MacCoun in the Annual Review of Psychology 1998 49:259-287 (available in html format here or pdf format here). Read MacCoun's article and it will change the way you interpret research.
There's so much more to talk about: academic-industry partnerships raise serious issues about the objectivity of academic research. There are also non-financial conflicts of interest (note Hammerschimdt 1995 J Lab Clin Med article, When commitments and interests conflict. "There's probably no greater conflict of interest than an NIH grant". [Medline]). Also, when emotions on an issue run high, claims of conflict of interest are often wielded as weapons of war. There is also serious bias in the selection of references in the bibliography of some research articles.
Returning to the original book review, you should note that the author of the book being reviewed, Sheldon Krimsky, has many journal publications on this topic and much of this material is available on the web in pdf format.
Conflict of interest and cost-effectiveness analysis. S. Krimsky. Jama 1999: 282(15); 1474-5. [Medline] [PDF]
Journal Policies on Conflict of Interest: If this Is the Therapy, What's the Disease? Sheldon Krimsky. Psychotherapy and Psychosomatics 2001: 70155-117. [Medline] [PDF]
Financial interests of authors in scientific journals: a pilot study of 14 publications. S. Krimsky, L. S. Rothenberg, P. Stott, G. Kyle. Sci Eng Ethics 1996: 2(4); 395-410. [Medline] [PDF]
Scientific journals and their authors' financial interests: a pilot study. S. Krimsky, L. S. Rothenberg, P. Stott, G. Kyle. Psychother Psychosom 1998: 67(4-5); 194-201. [Medline] [PDF]
You can find an earlier version of this page on my original website.