Based on past research (Mallinckrodt et al., 2005;McGrath et al., 2008) the researchers expect that the DSM-IV definition of melancholic depression be present in anywhere between 15 to 50% of the sample. This potential imbalance in group size is not problematic for the planned analytic strategy using Cox regression models (unlike having unequal sample sizes in ANOVA, for example - please see below for a more detailed description of the planned analysis) unless there are empty cells in the model (e.g., no responders in the "nonmelancholic" group). This would preclude the estimation of a model, although it would still be clinically useful information.