Medical literature has overstated the benefits of talk therapy for depression, in part because studies with poor results have rarely made it into journals, researchers reported Wednesday.

Their analysis is the first effort to account for unpublished tests of such therapies. Treatments like cognitive behavior therapy and interpersonal therapy are indeed effective, the analysis found, but about 25 percent less so than previously thought.

Doctors have long known that journal articles exaggerate the benefits of antidepressant drugs by about the same amount, and partly for the same reason — a publication bias in favor of encouraging findings. The new review, in the journal PLOS One, should give doctors and patients a better sense of what to expect from various forms of talk therapy, experts said, if not settle long-running debates in psychiatry about the relative merits of one treatment over another.

Five million to six million Americans receive psychotherapy for depression each year, and many of them also take antidepressant drugs, surveys find. Most people find some relief by simply consulting a doctor regularly about the problem, experts said. Engaging in a course of well-tested psychotherapy, according to the new analysis, gives them an added 20 percent chance of achieving an even more satisfying improvement, or lasting recovery. Before accounting for the unpublished research, that figure was closer to 30 percent, a difference that suggests that hundreds of thousands of patients are less likely to benefit.