Change mechanisms in psychotherapy: multiperspective assessment and relation to outcome.

The study aimed at constructing a reliable and valid post-session questionnaire measuring general change mechanisms of psychotherapy with correspondent versions for patient and therapist perspectives. Therefore, 253 inpatients in early, middle, and late stages of psychotherapy completed the newly developed Scale for the Multiperspective Assessment of General Change Mechanisms in Psychotherapy (SACiP) and diverse outcome measures. The psychometric qualities of the SACiP were excellent as shown by (a) exploratory factor analyses on patient and therapist ratings, (b) confirmatory factor analyses on later measuring times, and (c) high internal consistencies. Supporting construct validity, the SACiP predicted outcome, as shown by correlational analyses and mixed effects modeling. Patient evaluations of change mechanisms were better predictors of outcome than the corresponding therapist evaluations.