The process of change in psychotherapy: Common and unique factors

As a field, psychotherapy has long been dominated by the different types (or orientations) of psychological therapies in practice. Though there are hundreds if not thousands of different kinds of psychotherapy, in many ways some are quite similar—they share some common factors. In other ways, each orientation may possess some unique elements, or combinations of elements not found in most other kinds of therapy: unique factors. In this chapter, we describe how the theoretical and empirical discussions of common and unique factors have progressed historically, highlighting major contributions in identifying and organizing the influential components and active ingredients of psychotherapy. It can be shown that both common factors and more unique factors can be reliably identified, and that these factors can be linked with outcome, and may both be necessary to the successful application of any psychological therapy. Ultimately, the distinction between “common” and “unique” factors may be a false dichotomy when comparing many face-to-face psychotherapies, because neither common factors nor unique factors can exist without the other. Common factors rely on specific treatments, and unique factors exist in the context of common variables.