Dissociative symptoms as measured by the Cambridge Depersonalization Scale in patients with a bipolar disorder

Background: The Cambridge Depersonalization Scale (CDS) characterizes the quality, frequency, and duration of dissociative symptoms. While the psychometric properties of the CDS have been evaluated in primary dissociative disorder, this has been insufficiently addressed among other psychiatric patient groups such as patients with a bipolar disorder (BD). Methods: Outpatients with variable mood (n = 73) responded to a survey that assessed dissociative symptoms and other characteristics. We used factor analysis and McDonald's omega to evaluate psychometric properties of the CDS, and correlations with other characteristics. Results: Previously suggested multifactorial models of the CDS were not supported, but the single-dimensional model fit both dichotomized (p = 0.31, CFI = 0.99, RMSEA = 0.02, ECV 70%) and trichotomized CDS responses (p = 0.06, CFI = 0.96, RMSEA = 0.04, ECV 47%). The CDS showed high internal consistency (omega = 0.96). CDS factor scores correlated with symptom severity on the Quick Inventory for Depressive Symptoms (QIDS-SR-16) (rho = 0.59), the Social Phobia Inventory (rho = 0.52), the American Association of Psychiatry Severity measure for Panic Disorders (rho = 0.46), the Childhood Trauma Questionnaire (rho = 0.44), and the Trauma Screening Questionnaire (rho = 0.53). Two abbreviated versions of the CDS, retaining the best 14 or 7 items were proposed. Limitations: The sample size remained moderate. Conclusions: The CDS is a psychometrically sound, unidimensional measure with clinical impact to detect and characterize dissociative symptoms in BD patients. Establishing the reliability and validity of the abbreviated scales for screening necessitates further study.