Delusional depressions: natural history and response to treatment.

A review of the abundant literature concerning the distinction between delusional and non-delusional depressions, especially of the work of Aubrey Lewis, reveals that before the introduction of specific therapies most in-patients with major depressive illness eventually recovered; the small percentage who did not almost all came from the delusional group. The dichotomy lost its clinical significance after the introduction of ECT, as both groups were equally responsive. However, accumulating evidence indicates that unipolar delusional depressives are significantly less responsive to tricyclic anti-depressant therapy than non-delusional depressives. The presence or absence of delusional thinking should be considered as a significant criterion in the classification of depressive disorders, and the presence or absence of delusional thinking should influence the choice of treatment for severely depressed patients.