Clinical Trial Registration Law Prevents Cherry Picking Medical Results: Lowered Reported Positive Treatment Effects From 57 Percent To 8 Percent: Raises Question Of Accuracy of Medical Treatment Studies Prior To The Year 2000

From Nature, Research Highlights, "Registered clinical trials make positive findings vanish: A study showing a fall in positive trial results after the roll-out of clinicaltrials.gov attracted much attention on social media." by Chris Woolston:

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. Study author Veronica Irvin, a health scientist at Oregon State University in Corvallis, says this suggests that registering clinical studies is leading to more rigorous research. Writing on his NeuroLogica Blog, neurologist Steven Novella of Yale University in New Haven, Connecticut, called the study “encouraging” but also “a bit frightening” because it casts doubt on previous positive results.***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.