How to assess the onset of antidepressant effect: Empirical data on 2788 patients

In this study the data of 2788 patients suffering from major depressive disorder and treated with either placebo or 7 different antidepressants in randomized controlled trials were used to detail the individual time characteristics of antidepressant drug response.

More than 50% of all patients showed improvement (≥20% decrease of HAMD scores, subsequently sustained) within the first 2 weeks of treatment. Improvement occurred in nearly 70% of the improvers within the first 2 weeks (early improvement). Early improvement turned out to be highly predictive of later outcome, with more than 70% of early improvers becoming treatment responders, and less than 25% of non-improvers by the end of week 2 becoming later responders.

These data suggest that early improvement represents an important clinical indicator of later response to drug treatment in acute depression. The absence of early improvement implies little chance of a sufficient subsequent response.