Is the Impact of Psychotherapy Processes on Outcomes Already Quacking and Waddling? Comment "A Primer on Psychotherapy Process Research (Pfeifer & Strunk, 2015)"

The article by Pfeifer and Strunk on psychotherapy process research offers a highly thoughtful review on the state of psychotherapy process research in cognitive therapy for depression, and the inherent challenges in establishing causal relationships between process and outcomes. In this commentary, I argue that the goal of internal validity in psychotherapy process research may be unattainable, and possibly unnecessary. Finally, I suggest that psychotherapy process research should shift from "does it affect change?" to "how does it affect change?", "when does it affect change?", and "for whom does it affect change?".