The paper addresses the differential effectiveness of 68 psychotherapists from 10 different types of psychotherapy. 237 caseloads of 68 therapists from 10 theoretically different treatment approaches were investigated in a naturalistic psychotherapy study in Switzerland. Outcomes for each of the 237 therapies were operationalised using the strategy of multiple outcome criteria (pre-post differences in the four outcome measures Brief Symptom-Inventory, Beck Depression Inventory II, Outcome Questionnaire 45-2, and Global Assessment Functioning Scale were transformed into T-scores and summed up for pre and post measurements).
A factor analysis of the change scores of the T-score sums resulted in a one-factor solution (Eigenwert 2.699). The factor scores of all patients seen by a therapist was then averaged for each therapist. The resulting 68 scores were subjected to a hierarchical cluster analysis which generated a three-cluster solution of differently effective therapists. The results document that three clusters of therapists emerged: predominantly successful therapists, therapists with mixed effectiveness, and therapists who are predominantly less successful.
The results clearly show that psychotherapists ‘effectiveness is not entirely determined by their personality alone, but rather by additional variables such as patients ‘severity of psychological problems at treatment entrance, by the quality of the therapeutic alliance, and obviously by therapists’ competence. Degree of professional experience, gender matchings, theoretical orientation, as well as formal diagnostical issues did not play a major role. Conclusions: The paper discusses possible explanations for psychotherapists ‘differential effectiveness and shows aspects for further research.
