In the study, the research team focused on drugs in the class known as Selective Serotonin Reuptake Inhibitors (SSRIs), which work by increasing levels of the mood controlling chemical serotonin in the brain. These included fluoxetine (Prozac), venlafaxine (Efexor) and paroxetine (Seroxat). The analyses revealed that even the positive effects seen on severely depressed patients were relatively small, and open to interpretation. The seemingly good result came from the fact that the patients in the study responded less to dummy pills, placebos, which they were given during trials, rather than any notable response to anti-depressants.
"The difference in improvement between patients taking placebos and patients taking anti-depressants is not very great," BBC quoted Professor Irving Kirsch, the study's lead author, as saying. "This means that depressed people can improve without chemical treatments.
"Given these results, there seems little reason to prescribe anti-depressant medication to any but the most severely depressed patients, unless alternative treatments have failed to provide a benefit," he added. Marjorie Wallace, head of the mental health charity Sane, said that if these results were confirmed they could be "very disturbing".
But the makers of Prozac and Seroxat, two of the commonest anti-depressants, said they disagreed with the findings. A spokesman for GlaxoSmithKline, which makes Seroxat, said the study only looked at a "small subset of the total data available". The study is published in the journal PLoS Medicine.