New analyses of the National Institute of Mental Health Treatment of Depression Collaborative Research Program: do different treatments reflect different processes?

To determine whether or not different therapies have distinct patterns of change, it is useful to investigate not only the end result of psychotherapy (outcome) but also the processes by which outcomes are attained. The present study subjected data from the National Institute of Mental Health Treatment of Depression Collaborative Research Program to survival analyses to examine whether the process of psychotherapy, as conceptualized by the phase model, differed between psychotherapy treatment approaches. Few differences in terms of progression through phases of psychotherapy were identified between cognitive behavior therapy and interpersonal therapy. Additionally, results indicate that phases of psychotherapy may not represent discrete, sequentially invariant processes.