Although improvement of clients' state is a central concern for psychotherapy, relatively little is known about how change in outcome variables unfolds during psychotherapy. Client progress may follow highly variable temporal courses, and this variation in treatment courses may have important clinical implications. By analyzing treatment progress using growth mixture modeling up to the 6th session in a sample of 192 outpatients treated under routine clinic conditions, the authors identified 5 client groups based on similar progress on the short form versions of the Clinical Outcomes in Routine Evaluation-Outcome Measure. The shapes of early change typical for these client groups were characterized by (a) high initial impairment, (b) low initial impairment, (c) early improvement, (d) medium impairment with continuous treatment progress, or (e) medium impairment with discontinuous treatment progress. Moreover, the shapes of early change were associated with different treatment outcomes and durations, and several intake variables (depression, anxiety, and age) enabled prediction of the shape of early change and/or prediction of individual treatment progress within client groups with similar shapes of change.
Stulz, N., Lutz, W., Leach, C., Lucock, M., & Barkham, M. (2007). Shapes of early change in psychotherapy under routine outpatient conditions. Journal of Consulting and Clinical Psychology, 75(6), 864-874. https://doi.org/10.1037/0022-006X.75.6.864