The Development and Psychometric Evaluation of the Group Schema Therapy Rating Scale - Revised.

Background: Recent research has supported the efficacy of schema therapy as a treatment for personality disorders. A group format has been developed (group schema therapy; GST), which has been suggested to improve both the clinical and cost-effectiveness of the treatment.

Aims: Efficacy studies of GST need to assess treatment fidelity. The aims of the present study were to improve, describe and evaluate a fidelity measure for GST, the Group Schema Therapy Rating Scale - Revised (GSTRS-R).

Method: Following a pilot study on an initial version of the scale (GSTRS), items were revised and guidelines were modified in order to improve the reliability of the scale. Students highly experienced with the scale rated recorded GST therapy sessions using the GSTRS-R in addition to a group cohesion measure, the Harvard Community Health Plan Group Cohesiveness Scale - II (GCS-II). The scores were used to assess internal consistency and inter-rater reliability. Discriminant validity was assessed by comparing the scores on the GSTRS-R with the GCS-II.

Results: The GSTRS-R displayed substantial internal consistency and inter-rater reliability, and adequate discriminate validity, evidenced by a weak positive correlation with the GCS-II.

Conclusions: Overall, the GSTRS-R is a reliable tool that may be useful for evaluating therapist fidelity to GST model, and assisting GST training and supervision. Initial validity was supported by a weak association with GCS-II, indicating that although associated with cohesiveness, the instrument also assesses factors specific to GST. Limitations are discussed.