Information for the study was gathered from six different placebo-controlled studies taking place across a 29-year span. It included data from 718 adult outpatients being treated for minor or major depressive disorder.

“The magnitude of benefit of antidepressant medication compared with placebo increases with severity of depression symptoms,” authors of the study explain, “and may be minimal or nonexistent, on average, in patients with mild or moderate symptoms.”

According to the New York Times, the success rate of placebos in some studies such as this can be as high as 50 percent for individuals with mild to moderate depression. People who continue to use antidepressants do appear to have a lower relapse rate, though—just one-third to one-half that of those taking placebos.

The study has its limitations, however. First of all, its conclusions are based on studies including just two different antidepressants. Another drawback is that, for the purpose of discovering which drugs are most effective, many studies of antidepressant medications exclude people who get better using placebos.

Finally, results may be limited because of the difficulty of finding studies that include people with mild to moderate depression, rather than just those with severe depression. A study with a much larger pool of participants would provide greater insight into the effectiveness of placebos versus antidepressants.

The study is merely suggestive, and neither proves nor disproves the claim that antidepressants are no more effective than placebos. In no way does it mean that someone should stop taking medication prescribed for depression. Rather, it provides something for antidepressant users to consider and discuss with their doctors.

“For patients with very severe depression, the benefit of medications over placebo is substantial,” authors concluded.

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