Drug-placebo difference: in antidepressant drug trials could be 50% greater than previously believed.

A pooled analysis of randomized placebo controlled antidepressant trials shows that the rate of antidepressant and placebo responders are 50% and 30% respectively. The traditional calculation of drug-placebo difference (50-30=20%) in these drug-trials is based on the assumption that all placebo responders should be antidepressant responders. However, it seems to be not the case, since about one-third of placebo responders are antidepressant nonresponders. Considering this, the fair calculation of antidepressant-placebo difference in randomized placebo controlled trials results in a 30% rather than 20% difference. The drug-placebo differences in all antidepressant drug trials should be re-calculated.