The benefits of talk therapy for depression are overstated, according to researchers.

They analyzed 55 studies funded by the U.S. National Institutes of Health between 1972 and 2008 and concluded that talk therapy is about 25 percent less effective than previously thought, The New York Times reported.

Specifically, talk therapy for depression is effective for about 20 percent of patients, rather than the previous figure of nearly 30 percent.

Talk therapy has been regarded as more effective than it actually is partly due to the fact that many studies with poor results were not published in journals, according to study leader Ellen Driessen, VU University in Amsterdam in the Netherlands, and colleagues.

Their findings were published Wednesday in the journal PLoS One.

Each year, five to six million Americans receive talk therapy for depression, The Times reported.