WASHINGTON: Patients with mild or moderate depression may benefit little from antidepressant medications and may be better treated with alternatives, researchers said Tuesday.

A group of researchers combined data from six studies involving 718 adult outpatients who ranged from mildly to very severely depressed according to the Hamilton Depression Rating Scale.

Their study, which sought to compare the benefits of commonly prescribed antidepressants (ADM) compared to placebos, was published in the Journal of the American Medical Association.

The authors, led by Jay Fournier of the University of Pennsylvania, Philadelphia, found that the effect of antidepressants varied considerably, depending on the severity of the symptoms.

"True drug effects (an advantage of ADM over placebo) were nonexistent to negligible among depressed patients with mild, moderate and even severe baseline symptoms, whereas they were large for patients with very severe symptoms," they wrote.

Most studies on antidepressants -- currently the standard treatment for major depressive disorders -- focus on the impact of the drugs on patients considered to be severely depressed, but there remains scant evidence on their effect for patients with less severe depression.

Advertisements for these drugs to clinicians or the general public omit this feature, the researchers noted.

The majority of patients receiving antidepressants in clinical practice have depression measures below the high level of symptom severity they found necessary for the drugs to have a meaningful impact, according to the study.

"Prescribers, policymakers and consumers may not be aware that the efficacy of medications largely has been established on the basis of studies that have included only those individuals with more severe forms of depression," the authors wrote.

"Efforts should be made to clarify to clinicians and prospective patients that whereas antidepressant medications can have a substantial effect with more severe depressions, there is little evidence to suggest that they produce specific pharmacological benefit for the majority of patients with less severe acute depression."