Harvard Men's Health Watch

When doctors disagree: How to cope with conflicting results

"Who shall decide," asked Alexander Pope, "when doctors disagree?" It's a good question, and it must have been a very common one in Pope's day, since in 1732 medical practice was based largely on tradition and opinion, not science.

In the 21st century, medicine is very much a science. As a result, careful research should provide clear answers that stand the test of time and the scrutiny of additional investigations. That's the theory behind evidence-based, data-driven scientific medicine. But in our imperfect world, things don't always turn out as they should. How often do major studies disagree with each other? Why does it happen? And what should you do about it?

Studying the studies

To study contradictory clinical research results, Dr. John Ioannidis focused on results published in three of the most prestigious general medical journals (The New England Journal of Medicine, Journal of the American Medical Association, and The Lancet) and in 17 top-quality medical specialty journals between 1990 and 2003. To concentrate on major, high-impact research, he analyzed only papers that had each been cited at least 1,000 times by subsequent medical publications.

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