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Tuesday, 28.03.2017

Martin Katz's reply to Lesley Morey's comment

Dr. Morey's analysis uncovered an error in our last response, i.e., the figure of 39% of patients responding, was incorrect. The request for calculating "positive" and "negative percentage predictions" (NPP) is also, understandable. We have, however, as he agrees, already well established that the negative predictive value (NPP) is about 90%. That means that the finding that an absence of early improvement in the patient almost certainly leads to non-clinical response at outcome of treatment, is essentially validated. I and my co-authors have acknowledged in a previous paper that this is a small study and requires a larger study for confirmation of all the results. The Stassen et al (1996) and Szegedi et al (2009) studies that involved thousands of patients essentially confirmed the large part of those results. We do not believe that the statistics recommended by Morey will add significantly to what has already been learned, and to avoid "overanalyzing" data from what was essentially a small study, are not inclined to conduct any further analyses.   


Stassen HH, Angst J, Delini-Stula A. Delayed onset of action of antidepressant drugs? Survey of recent results. Eur Psychiatry 1996; 12: 166-76.

Szegedi A, Jansen WT, van Wugenburg AP. Early improvement in the first two weeks as predictors of treatment outcome in patients with major depressive disorder: a met-anlysis including 6,562 patients. J clin Psychiatry 2009; 70:344-53

Martin M.  Katz
January 14, 2016