Electroconvulsive therapy of endogenous depression: an analysis of the influence of various factors on the efficacy of the therapy.

The influence of various factors on therapeutic efficacy was studied in 44 patients with endogenous depression and treated with E.C.T. Therapeutic efficacy was estimated by the rated outcome one week after four treatments and one week after the end of the course, and by the number of treatments required. The factors studied were age, sex, existence of cycloid personality traits, the presence of eliciting stress factors, number of previous depressions and of previous courses of E.C.T., interval to latest depression and latest E.C.T., and duration and severity of the present depression. None of the factors studied displayed any strong relationship to therapeutic efficacy. Cycloid patients required fewer treatments for a satisfactory therapeutic response. Further, the therapeutic response tended to appear later in old patients and when the interval from a preceding course of E.C.T. was short. The final outcome tended to be less favourable after a greater number of preceding courses of E.C.T.