The Cambridge Depersonalisation Scale: a new instrument for the measurement of depersonalisation

Existing self-rating scales to measure depersonalisation either show dubious face validity or fail to address the phenomenological complexity of depersonalisation. Based on a comprehensive study of the phenomenology of this condition, a new self-rating depersonalisation questionnaire was constructed. The Cambridge Depersonalisation Scale is meant to capture the frequency and duration of depersonalisation symptoms over the ‘last 6 months’. It has been tested on a sample of 35 patients with DSM-IV depersonalisation disorder, 22 with anxiety disorders, and 20 with temporal lobe epilepsy. Scores were compared against clinical diagnoses (gold standard) and correlated with the depersonalisation subscale of the Dissociation Experiences Scale (DES). The scale was able to differentiate patients with DSM-IV depersonalisation disorder from the other groups, and showed specific correlations with the depersonalisation subscale of the DES ( r=0.80; P=0.0007). The scale also showed high internal consistency and good reliability (Cronbach alpha and split-half reliability were 0.89 and 0.92, respectively). The instrument can, therefore, be considered as valid and reliable, and can be profitably used in both clinical and neurobiological research.