BOSTON Nearly a third of antidepressant drug studies are never published in the medical literature and nearly all happen to show that the drug being tested did not work, researchers reported on Wednesday.
In some of the studies that are published, unfavorable results have been recast to make the medicine appear more effective than it really is, said the research team led by Erick Turner of the Oregon Health & Science University.
Even if not deliberate, this can be bad news for patients, they wrote in their report, published in the New England Journal of Medicine.
"Selective publication can lead doctors to make inappropriate prescribing decisions that may not be in the best interest of their patients and, thus, the public health," they wrote.
The idea that unfavorable test results are quietly tucked away so nobody will see them -- sometimes call the "file drawer effect" -- has been around for years.
The Turner team used a U.S. Food and Drug Administration registry in which companies are supposed to log details of their drug tests before the experiments are begun.
"It tells you where they placed their bets before they saw the data," Turner said in a telephone interview.
Of the 74 studies that started for the 12 antidepressants, 38 produced positive results for the drug. All but one of those studies were published.
However, only three of the 36 studies with negative or questionable results, as assessed by the FDA, were published and another 11 were written as if the drug had worked.
"Not only were positive results more likely to be published, but studies that were not positive, in our opinion, were often published in a way that conveyed a positive outcome," said the authors.
For example, of the seven negative studies done on GlaxoSmithKline's Paxil, five were never published. The researchers found three studies for GSK's Wellbutrin SR, but the two negative ones never reached print.
There were five studies for Pfizer's Zoloft, but the three showing the drug to be ineffective were not published. A fourth study, ruled questionable by the FDA, was written and published to make it appear that the drug worked.
A Glaxo spokeswoman said the company posts the data from all of its trials, positive or negative, on the Internet.
"GlaxoSmithKline agrees that public disclosure of clinical trial results for marketed medicines is essential and fully supports registration of all trials in progress," she said.
"Pfizer is committed to the communication of results of all registered clinical studies, regardless of outcome. More specifically, we have committed to disclose clinical trial results within one year after study completion for all of our marketed products," Pfizer spokesman Jack Cox said in an e-mail.
Turner and his colleagues did not find out who was to blame for not publishing the studies. He said medical journals may have played a role by deciding they would rather publish favorable results.
"There's an expectation that if you get a positive result, that's what you're supposed to do, and if you get a negative result you have failed," said Turner. "The first impulse is to say, 'I was wrong. Maybe I should move on to something more interesting'" so the results may never get written up.
(Editing by Maggie Fox and David Wiessler)