Be careful believing what you read
August 31st, 2005 by Tom Johnson

Originally found on

On Negative Results

Posted by
David Appell at August 30, 2005 08:48 AM in Biotechnology and Health Care.

“There's a very interesting article by John Ioannidis in PLoS Medicine,
the free online journal. Most current published research findings might
well be false, he says. There are several factors, and I think it's
worth presenting them in detail:

1. Many research studies are small, with only a few dozen participants.

2. In many scientific fields, the “effect sizes” (a measure of how
much a risk factor such as smoking increases a person’s risk of
disease, or how much a treatment is likely to improve a disease) are
small. Research findings are more likely true in scientific fields with
large effects, such as the impact of smoking on cancer, than in
scientific fields where postulated effects are small, such as genetic
risk factors for diseases where many different genes are involved in
causation. If the effect sizes are very small in a particular field,
says Ioannidis, it is “likely to be plagued by almost ubiquitous false
positive claims.

3. Financial and other interests and prejudices can also lead to untrue results.

4. “The hotter a scientific field (with more scientific teams
involved), the less likely the research findings are to be true,” which
may explain why we sometimes see “major excitement followed rapidly by
severe disappointments in fields that draw wide attention.”

ought to be an eye-opener…. The solution? More publication of
preliminary findings, negative studies (which often suffer that fate of
file-drawer effect),
confirmations, and refutations. PLoS says, “the editors encourage
authors to discuss biases, study limitations, and potential confounding
factors. We acknowledge that most studies published should be viewed as
hypothesis-generating, rather than conclusive.” And maybe this will
temper journalists' tendency to offer every new study as the Next Big

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