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In a meta-analysis of six prior studies on both the older tricyclic and the newer selective serotonin reuptake inhibitor (SSRI) antidepressants, the researchers found that the less severe the depression, the less effective the drug. The sample included 434 patients who were taking antidepressants and 284 who were getting a placebo.
"The magnitude of benefit of antidepressant medication compared with placebo increases with severity of depression symptoms and may be minimal or nonexistent, on average, in patients with mild or moderate symptoms," the researchers wrote.
The study did suggest that antidepressants might be more effective than a placebo in some cases of severe depression. Dr. Gary Kennedy of the Albert Einstein College of Medicine questioned this finding, however.
"The finding that more severe depression is more likely to respond to antidepressant medication seems sound," he said. "But only six studies were used to generate the conclusion, and three of those studies used an antidepressant that few practicing physicians would prescribe nowadays."
Dr. Richard Besser, chief medical editor for Good Morning America, noted that patients in the study improved noticeably with both placebo and antidepressant treatment.
"What you can't tell from this study is what else is going on," he said. "Were these individuals getting what is most effective, which is talk therapy?"
According to Besser, simply participating in the study meant that patients were indeed getting this form of treatment.
"The most effective thing for mild to moderate depression is being in a therapeutic relationship where they can talk through their problems with someone who is really skilled," Besser said. "What they found ... is that it didn't really matter the drug. You were getting better if you had [talk therapy] and that should give people hope."
