Researchers led by Irving Kirsch of the University of Hull reviewd a series of studies, both published and unpublished, on four antidepressants, they were "Prozac", a/k/a "Fluoxetine" manufactured by Eli Lilly & Co.; "Effexor", a/k/a "Venlafaxine" manufactured by Wyeth's; "Paxil" a/k/a "Seroxat or Paroxetine" manufactured by GlaxoSmithKline's, and "Serzone" a/k/a "Nefazone" manufacted by Bristol-Myers Squibb Co.. The study examined the question of whether a person's response to these drugs hinged on how depressed they were prior to obtaining treatment. The researchers found that compared with placebos, these new-generation antidepressant medications did not yield clinically significant improvements in depression in patients who initially had moderate to severe depression. The study found that significant benefits occurred only in the most severely depressed patients. " Drug-placebo differences in antidepressant efficacy increase as a function of baseline severity, but are relatively small even for depressed patients. The relationship between initial severity and antidepressant efficacy is attributable to decreased responsiveness to placebo among very severly depressed patients, rather to increaseed responsiveness to medication", the rearchers wrote. " Although patients get better when they take antidepressants, they also get better when they take a placebo, and the differance in improvement is not very great. This means that depressed people can improve without chemical treatments," Irving Kirsch said in a statement. Mary Ann Rhyne, a spokesperson for GlaxoSmithKline's, said the study only took into account the data submitted prior to the drug's U.S. approval.