Publication bias

Publication bias refers to differences between studies that get published in medical journals and those that do not. A 1991 study published in the Lancet compared published to unpublished research. Investigators found those studies that were positive, meaning they generated statistically significant results, were more than twice as likely to be published as those that did not find significant differences between the treatment and control groups.

The result of publication bias is that the body of studies available in medical literature may portray a drug or treatment as being more effective than it actually is. Systematic reviews of drug or treatment effects often try to control for publication bias. Publication bias is part of a larger group of factors that may skew study reviews called reporting biases.