A January 2008 study published in the New England Journal of Medicine reveals that nearly one-third of studies conducted on antidepressant drugs are not published. Nearly all of the unpublished studies show that the drugs being tested didn’t work. In addition, some of the studies on antidepressants that were published spun unfavorable results to make the drugs appear more effective than they really were.

The United States Food and Drug Administration (FDA) does not require companies to publish all data on clinical trials or to make those trials publicly available. However, “[s]elective 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,” wrote the authors of the study.

The report focused on 74 studies conducted on 12 antidepressants. Thirty-eight of the studies had favorable results, all but one of which were published. But there were 36 studies that had negative or questionable results, and only three of those studies were published. An additional 11 studies with negative or questionable results were published, but were written as if there were positive results.

“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,” wrote the authors.

For example, GlaxoSmithKline’s (GSK) antidepressant Paxil had seven negative studies, five of which were never published. In addition, GSK’s Wellbutrin had three studies, two of which were negative and never published.

Pfizer also had five studies conducted on its drug Zoloft, but three studies that showed the ineffectiveness of the drug were not published. A fourth questionable study was written and published to make it look like the drug worked.

The study is significant because allowing companies to publish only positive studies of antidepressants may allow them to make inflated claims about the efficacy of the drugs, thus making it virtually impossible for doctors and patients to know how effective or ineffective the drugs are. It can also hide data on side effects of drugs.

Dr. Thomas P. Laughren, director of the division of psychiatry products at the FDA, said the agency has known favorable studies are more likely to be published for a long time.

“It’s a problem we’ve been struggling with for years,” Laughren said.

Sources: Benedict Carey, “Antidepressant studies unpublished,” New York Times, January 17, 2008; Gene Emery, “Unfavorable drug studies don’t get into print: report,” Reuters.com, January 17, 2008; “Pharma companies hid antidepressant data,” Furious Seasons, January 17, 2008.