A study in the journal PLoS Medicine found that popular antidepressants aren't much better at treating depression than placebos. More precisely, both placebos and antidepressants influenced significantly patients for the better. Those who took real drugs such as Prozac from Eli Lilly, Paxil from GlaxoSmithKline and Zoloft from Pfizer felt only slightly better than those taking placebos, and as such the overall difference between the drug group and the placebo group was less than the minimum generally considered clinically significant, the study has found.

The researchers, led by Dr Irving Kirsch, from the University of Hull, have analyzed all the available full data sets from all clinical trials, published or unpublished, submitted to the US Food and Drug Administration (FDA) for licensing four of the new generation of antidepressants: fluoxetine (Prozac), venlafaxine (Effexor), nefazodone (Serzone), and paroxetine (Seroxat, Paxil).

All four drugs are SSRIs, selective serotonin reuptake inhibitors. The difference was slightly larger when the patients were severely depressed, but it was still not very significant. The study is titled "Initial Severity and Antidepressant Benefits: A Meta-Analysis of Data Submitted to the Food and Drug Administration."

"The difference in improvement between patients taking placebos and patients taking anti-depressants is not very great," said Professor Irving Kirsch of Hull University, in northern England, who led the team, quoted by AP. "This means that depressed people can improve without chemical treatments."

Drug makers rushed to contain damage to their future sales. Eli Lilly, GlaxoSmithKline and others involved in the antidepressants market rushed out statements upholding the effectiveness of their SSRIs.