The phase model of psychotherapy outcome: Domain-specific trajectories of change in outpatient treatment.

In the present study, the predictions of the Phase model concerning multidimensional phases were validated. The finding that trajectories of change are not uniformly log-linear, but either log-linear or linear in a domain-specific manner, is partly inconsistent with the model. Clinical or methodological significance of this article: This article extends previous research in the field of psychotherapeutic change by providing results from the modeling of change trajectories in psychotherapeutic treatments with larger amounts of sessions (i.e., more than 20 sessions). Our findings of domain-specific different shapes (i.e., log-linear for Well-Being and Symptoms and linear for Interpersonal functioning) and speed (i.e., fastest for Well-Being and slowest for Interpersonal function) of trajectories of psychotherapeutic change may be clinically applied by means of guidelines for therapists to plan and adapt their treatments. In addition to content-related aspects of a continuous adjustment of treatment goals (e.g., merely symptom-oriented or focusing on interpersonal change) and interventions, this adaptive planning is also related to health care considerations (e.g., may justify longer treatments if therapy goals target several domains of change).