Multiple measures, methods, and moments: a factor-analytic investigation of change in depressive symptoms during acute-phase cognitive therapy for depression

Background. Researchers and clinicians use a variety of measures to assess depressive symptoms, including clinician reports [for example the 17-item Hamilton Rating Scale for Depression (HRSD17) and the 30-item Inventory for Depressive Symptomatology - Clinician Report (IDS-C-30)]; and patient reports [for example, the Beck Depression Inventory (BDI) and the 30-item Inventory for Depressive Symptomatology - Self-Report (IDS-SR-30)]. Although their concurrent convergent validity is well established, the degree to which these measures reflect the same pattern and level of change during treatment is unclear. Method. We assessed depressive symptoms with two clinician (HRSD-17, IDS-C-30) and two patient (BDI, lDS-SR-30) reports on 14-15 occasions in 127 out-patients with recurrent major depressive disorder treated with 20 sessions of acute-phase cognitive therapy. Results. Factor analyses revealed that time was the major source of variation in depressive symptom severity and change, with distinct 'early' and 'late' assessment factors, regardless of measure or rater (patient v. clinician). Average symptom severity decreased rapidly on all measures until mid-treatment, after which gradual decreases continued through the end of treatment. Effect sizes for pre- to post-treatment change were large for all measures (d= 1-9-2-2), although there were significant differences among measures at some time-points. Conclusions. The HRSD-17, BDI, IDS-C-30 and IDS-SR-30 reflect essentially the same symptom severity and change constructs during acute-phase cognitive therapy. Clinicians and researchers using one of these measures may estimate scores on the others with the provided common-factor conversions.