via nature.com, Registered clinical trials make positive findings vanish
The launch of the clinicaltrials.gov registry in 2000 seems to have had a striking impact on reported trial results, according to a PLoS ONE study1 that many researchers have been talking about online in the past week.
A 1997 US law mandated the registry’s creation, requiring researchers from 2000 to record their trial methods and outcome measures before collecting data. The study found that in a sample of 55 large trials testing heart-disease treatments, 57% of those published before 2000 reported positive effects from the treatments. But that figure plunged to just 8% in studies that were conducted after 2000….
…Irvin says that by having to state their methods and measurements before starting their trial, researchers cannot then cherry-pick data to find an effect once the study is over. “It’s more difficult for investigators to selectively report some outcomes and exclude others,” she says….
“Loose scientific methods are leading to a massive false positive bias in the literature,”