The Multiple Self-States Model (MSSM) of Cognitive Analytic Therapy (CAT) conceptualizes identity disturbances in personality, particularly borderline personality disorder. The Personality Structure Questionnaire (PSQ) has been devised to measure deficits in personality integrity and represent an assessment measure of the MSSM. A spectrum of multiplicity in the self and dissociation is implied within the MSSM with gradation from borderline personality to dissociative identity disorder. The construction, psychometric properties, reliability, validity and clinical utility of the PSQ as a measure of the MSSM are described based on data from the present study and that of Broadbent, Clarke and Ryle (The Personality Structure Questionnaire: a brief self-report measure of personality integration. Unpublished manuscript) and its relationship to psychological constructs of identity integrity is investigated. A series of non-clinical and clinical groups of participants were administered the PSQ and other standardized measures. The PSQ was shown to be a reliable self-report measure and factor analysis revealed it to be unidimensional and to correlate convergently
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P. Pollock et al.with multiplicity, dissociation and constructs related to identity disturbance. Regression analysis indicated the PSQ to be predicted by greater multiplicity. The PSQ, in combination with other constructs, also discriminated between diagnosed clinical groups (psychotherapy patients, borderline personality disorder and dissociative identity disorder). The PSQ is shown to be a brief, psychometrically sound self-report measure of identity disturbance as conceptualized by the MSSM in CAT. The applicability of the PSQ and its relevance to the concepts of multiplicity and dissociation within the MSSM of CAT are discussed.