Biological markers for endogenous depression in series and parallel.

Several authors have shown that endogenous depressed patients have biological abnormalities which exist to a lesser extent in nonendogenous depressives and in normals, and have suggested that these biological abnormalities may be used as markers to classify depressed patients as endogenous or nonendogenous. We have investigated several of these biological abnormalities, and have explored the diagnostic classifications based on individual markers and on two or more markers in combination. The evaluation of combinations of diagnostic tests requires different statistical techniques than does the evaluation of single tests, and we discuss two such techniques: stepwise multiple regression and contingency table analysis. We report here our results with the dexamethasone suppression test (DST), EEG studies of sleep, and the amphetamine-stimulated release of growth hormone separately and in combination. The amphetamine-stimulated release of growth hormone was not diagnostically useful.