Background: While highlighting the efficacy of different treatments for major depressive disorders (MDD), findings of the National Institute of Mental Health (NIMH) Treatment of Depression Collaborative Research Program (TDCRP) often are interpreted as supporting the idea of treatment non-specificity for MDD. However, heterogeneity in treatment courses and outcomes might be undetected when focusing only on types of treatment in terms of sample means without taking into account early change in treatment.
Method: In this study, growth mixture models (GMM) were used in the completer sample of N=162 patients from the NIMH TDCRP to identify meaningful patterns of early change of depression severity that are shared by many individual patients.
Results: Results revealed three typical patterns of early change over the first 8 weeks of treatment irrespective of the type of treatment protocol provided: (a) moderate to severe depression with moderate early improvement, (b) moderate to severe depression with rapid early improvement, and (c) mild to moderate depression with moderate early improvement. In contrast to the type of treatment, these differential patterns of early response (together with overall pre-treatment symptom severity) predicted outcomes (i.e. depression severity) at treatment termination and over the 1.5-year follow-up period.
Limitations: Due to the small sample size and the controlled setting of this study the degree to which these results can be generalized to clinical practice has to be further investigated.
Conclusions: The findings provide further support for the assumption that early change is an important factor for the prediction of short- and long-term outcome in psychotherapy.