Toward a generalizable model of symptoms in major depressive disorder

Background: This study has two goals: 1) to establish a generalizable model of the symptoms observed in outpatients with major depressive disorder (MDD); and 2) to compare symptom coverage of the Inventory of Depressive Symptomatology, Clinician-Rated (IDS-C) and Self-Report (IDS-SR) to that of the Hamilton Depression Rating Scale (HDRS) and Beck Depression Inventory (BDI). Methods: A factor analysis of IDS-C, IDS-SR, HDRS, and BDI items was carried out on 324 adult outpatients with MDD. Patients with coexisting Axis I or III illness or those taking psychotropic medication were excluded. Results: Ten primary factors were identified, six of which were substantially intercorrelated, defining a second-order factor of general depression severity. Schmid–Leiman orthogonalization identified the symptoms most associated with general severity. Conclusions: The IDS provided more complete factor coverage than did the HDRS or BDI and thus may be more useful in research on symptom profiles.