According to an article in the New England Journal of Medicine ( NEJM), studies on antidepressants showing negative results are published less frequently than studies that show positive results -- and the underrepresentation may be generating a false sense of how effective these drugs are.

"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 of "Selective Publication of Antidepressant Trials and Its Influence on Apparent Efficacy."

The authors obtained Food and Drug Administration reviews for studies on 12 antidepressants -- 74 FDA-registered studies in total -- and then considered how many and what type were published. Notably, only one of the 37 that were viewed by the agency as having positive results was not published, while 22 of the 37 studies that were considered to have negative results were not published. And 11 others that the FDA asserted were negative were published in a way that the authors felt conveyed positive (and potentially misleading) results.

The NEJM article notes that the 11 studies were ones in which the primary outcome was nonsignificant but the publication "highlighted a positive result as if it were the primary outcome." Worse yet, nine of the articles omitted the non-significant result for the primary outcome altogether, according to the authors.

Thus, published literature suggested that 94% of studies were positive, but in actuality the figure was closer to 51%.

The research team, led by former medical reviewer for the FDA Erick Turner, M.D., said there could be many reasons the articles weren't published, and the team couldn't determine whether the publishing bias was due to authors or sponsors not submitting manuscripts or journal editors and reviewers not publishing them, or both.

Of course, "Selective reporting of clinical trial results may have adverse consequences for researchers, study participants, health care professionals, and patients," notes the article.

Big Pharma names Wyeth ( WYE), Pfizer ( PFE) and Eli Lilly ( LLY), each of which market antidepressants, were ticking downward in post-market trading Wednesday. Wyeth, which closed the day in positive territory, gave up 1.6% to $46.14 in recent after-hours trading, while Pfizer, which ended the regular session down 0.8%, fell another 0.4% in recent after-hours trading. Lilly, which ended the day down 0.9%, continued falling another 1.9% to $55 in post-close trading.