Research putting antidepressants in a positive light is more likely to make it into medical journals than that with negative outcomes, suggests a report in the New England Journal of Medicine.

The researchers, led by Erick Turner, former medical reviewer for the US Food and Drug Administration, looked at studies of 12 approved antidepressants registered with US regulators - including GlaxoSmithKline’s Paxil (paroxetine) and Pfizer’s Zoloft (sertraline) - and conducted a “systematic literature search” to seek out any matching publications.

Out of 74 FDA-registered studies, 31% were not published in medical journals. However, it was found that, out of 37 studies viewed by US regulators as positive, just one was not published, while those with “negative or questionable” outcomes were, with three exceptions, either not published (22 studies) or tailored to suggest a positive outcome (11 studies).

“According to the published literature, it appeared that 94% of the trials conducted were positive. By contrast, the FDA analysis showed that 51% were positive”, the researchers said, highlighting the bias.

While it is impossible to determine whether this bias was the result of researchers failing to submit their papers or editorial favourtism towards positive outcomes, the study’s authors stress that “selective publication of clinical trials - and the outcomes within those trials - can lead to unrealistic estimates of drug effectiveness and alter the apparent risk–benefit ratio”.