The effectiveness of psychotherapy in the treatment of major depression is apparently overstated, according to a group of researchers, Medical Daily reported.

The researchers said that many psychologists have failed to submit their works for assessment and that 25 percent of data on the effectiveness of talk therapy has not been published. If taken into consideration, this data would show that, contrary to popular belief, psychotherapy is actually not as effective in treating people with depression.

"This doesn't mean that psychotherapy doesn't work," study author Steve Hollon, Gertrude Conaway Vanderbilt Professor of Psychology, said in a press release. "Psychotherapy does work. It just doesn't work as well as you would think from reading the scientific literature."

Hollon said that this is because clinical studies that show positive outcomes regarding depression treatment are mostly the ones getting published, whereas those with not-so-positive outcomes are overlooked. He likened the process to "flipping a bunch of coins and only keeping the ones that come up heads."

The researchers gathered information on clinical trials of depression treatments conducted from 1972 to 2008 that were funded by the U.S. National Institutes of Health and found that about 25 percent of them were not published. After analyzing the results of both published and unpublished studies, the researchers found that the effectiveness of psychotherapy in treating depression was overemphasized because of publication bias.

Study co-author Erick Turner, associate professor of psychiatry and pharmacology at Oregon Health and Science University School of Medicine, said that the process of choosing articles for journal publications has loopholes.

"Journal articles are vetted through the process of peer review, but this process has loopholes, allowing treatment benefits to be overstated and potential harms to be understated," Turner said. "The consumers of this skewed information are health care providers and, ultimately, their patients."

"[W]e doubt that simple exhortations to authors or editors will do enough to change behavior. Instead, we join with others who recommend that funding agencies or journals should archive both original protocols and raw data from any funded randomized clinical trial," the authors wrote.

The study was published in the Sept. 30 issue of the journal PLOS One.