Measurement of Change with the Short Form of the OPD Structure Questionnaire (OPD-SQS)

Abstract

The transdiagnostic concept of personality structure plays a key role in psychodynamic nosology, since many mental and psychosocial disorders are considered mainfestations of structural vulnerabilities and deficits. Therefore, structural diagnostics is of particular importance, especially with respect to the planning of tailor-made psychotherapeutic interventions. Because changes in personality structure are increasingly being considered as a relevant therapeutic goal, any measures employed towards achieving this goal should be sensitive enough to capture these changes appropriately. Although the short form of the OPD Structure Questionnaire (OPD-SQS) can easily be administered and is therefore frequently used in clinical and research settings, its sensitivity to change has not yet been analyzed. Two large, independent and diagnostically heterogeneous samples of inpatient psychotherapy patients (n=1183 and n=967, respectively) completed the OPD-SQS both at admission and before discharge. Standardized Effect Size (SES), Standardized Response Mean (SRM) and Smallest Real Difference (SRD) were computed as indicators of the measure's ability to capture change. For the OPD-SQS and its subscales, low effect sizes were found in both samples (SES between 0.23 and 0.48; SRM between 0.27 and 0.53). Additionally, it was demonstrated that greater changes among patients with structural deficits were detectable with the OPD-SQS compared to those without structural deficits, and that these group differences were significant. By means of the SRD, we determined a proportion of about 22% of patients with significantly structurally improved changes in both samples. Despite some methodological issues, our findings suggest that the OPD-SQS is suitable for measuring changes in personality structure in inpatients between the beginning and the end of treatment. Since studies on the sensitivity to change of similar assessment tools are still pending, it is not yet possible to formulate any empirically validated recommendations as to which of the measure best captures therapeutically induced changes in personality structure.