Since Aubrey Lewis' classic study there has been debate about whether the distinction between depressive subtypes is categorical or dimensional.1-6 A recent article by Kendler et al7 supports a categorical classification of depressive subtypes. Using a different means of validating nosological distinctions, our group reached similar conclusions and we think it relevant to review the similarities and differences between our findings and those of Kendler et al.
In a prospective epidemiological study of adult female twins, Kendler et al used latent class analysis and identified 3 depressive subtypes—mild typical, atypical, and severe typical depression. Subjects with atypical depression were characterized by reversed vegetative depressive symptoms (overeating and oversleeping). These groups differed on many validating criteria, supporting a categorical distinction.
We reached a similar conclusion using psychopharmacologic dissection, a distinctly different method.8 In a series of 6 studies, patients with nonautonomous mood were randomized to receive imipramine, phenelzine,