Comparing the onset of action of antidepressants: Comparison of different criteria applied to the same data set

The issue of early onset of action (EOA) of an antidepressant was addressed by several authors. Unfortunately so far there is neither consensus nor convention on the definitions of EOA, or on measures and methods of assessments. There are several quite different approaches to the statistical analysis of the data. Our objective was to compare the results concerning EOA obtained by different statistical techniques applied on a data set which was generated by several independent conclusive double-blind, placebo controlled randomised trials with two antidepressants. The following statistical techniques were used: 1) statistically significant difference for the first time; 2) statistically significant and clinically relevant difference for the first time; 3) pattern analysis; 4) classical survival analysis without 'sustained response'; 5) survival analysis with sustained response. The advantages and drawbacks of different methods are discussed.