The factor structure of the Center for Epidemiological Study - Depression Scale in people with multiple sclerosis

Background: Depression is common in multiple sclerosis (MS); however, its assessment is complicated by biological processes. In this context it is important to consider the performance of depression screening measures including that their factor structure is consistent with expectation.  This study sought to identify the factor structure of the Center for Epidemiological Study - Depression Scale (CES-D) in people with MS (PwMS). Methods: Participants (N = 493) were those who had consented to take part in a large three-phase longitudinal study of depression in PwMS. CES-D questionnaires completed at phase 1 of the study were utilised. An error in the questionnaire meant it was most appropriate to consider data for 19 of the 20 CES-D questionnaire items. The data was split into two samples by a random selection process to create an exploratory, model development sample and a validation sample. The first sample was subject to confirmatory factor analysis. Following examination of model fit and specification errors, the original model was modified. The revised model was tested in the confirmation sample to assess reproducibility. Results: The analysis results supported the original four factor solution for the CES-D, that is: Depressed Affect, Positive Affect, Somatic Complaints/Activity Inhibition, and Interpersonal Difficulties. Conclusions: The CES-D appears to have a coherent structure with which to examine depression in PwMS.