IDS-C and IDS-SR: Psychometric properties in depressed in-patients

Sixty-eight depressed in-patients were assessed at admission (D0), and after 5 days (D5), ten days (D10) and 28 days (D28) of antidepressant treatment, with the Inventory for Depressive Symptomatology-Clinician (IDS-C) and the Inventory for Depressive Symptomatology-Self-Rated (IDS-SR) (Rush et al., 1986), the Montgomery and Asberg Depression Rating Scale (MADRS) (Montgomery and Asberg, 1979) and the depression factor of the Symptom Check List (SCL-90R) (Derogatis, 1977), in order to assess IDS-C and IDS-SR psychometric properties in depressed in-patients and to compare IDS-C to MADRS and IDS-SR to the SCL-90R depression factor. Most of the IDS-C and IDS-SR items were significantly correlated to the final score and the Cronbach alpha coefficients were high (0.75 for the IDS-C and 0.79 for the IDS-SR). Principal Component Analyses (PCA) showed three factors for both IDS-C and IDS-SR: ‘depression’, ‘anxiety/arousal’ and ‘sleep/appetite’. These results suggest satisfactory internal consistency of IDS-C and IDS-SR. Concurrent validity of the IDS-C with the MADRS was high (r=0.81), as well as concurrent validity of the IDS-SR with the SCL-90R depression factor (r=0.84). Concerning sensitivity to change, the four scales were able to discriminate between different levels of severity of depression. Moreover, considering paired t-tests on score changes, IDS-C sensitivity to change may be higher than MADRS sensitivity to change, this phenomenon being related to the number of items and degrees but not to the item contents. Contrary to IDS-C and MADRS, IDS-SR and SCL-90R depression factor were not different in terms of sensitivity to change. Finally, psychometric properties of IDS-C and IDS-SR in depressed in-patients are satisfactory and close to those obtained in depressed out-patients. The high sensitivity to change of the IDS-C may be an advantage for this scale as compared to the MADRS, especially in antidepressant drug trials.