Study 1 included 150 outpatients of 14 psychotherapists. Controlling for diagnosis, gender, and age, patients were randomized to a therapy group (n=75) or a waiting-list control group (n=75). After three months of waiting or psychotherapy, all subjects completed the "Questionnaire of Personal Changes", consisting of 12 temporal comparatively formulated items. Group comparisons indicate the change sensitivity of the items and the scale score for psychotherapeutic effects.
Study 2 followed a naturalistic design including 275 psychotherapy outpatients who completed the questionnaire 14-20 weeks after start of therapy.
Results confirm acceptable psychometric properties of the scale with reference to item parameters and reliability. Convergent validity of the scale score is empirically supported by significant correlations to clinically relevant indicators of psychotherapeutic outcomes from indirect measurements of change.