A review of the psychotherapeutic 'common factors' model and its application in physical therapy: the need to consider general effects in physical therapy practice.

This article explores the common factors model of psychotherapeutic intervention and discusses its relevance for physical therapy practice. The model provides an explanation for why the effects associated with specific technical approaches only minimally explain successful psychotherapy clinical outcomes. It postulates that factors common across diverse interventions (i.e. 'nonspecific' mechanisms) are responsible for a larger component of treatment efficacy. We outline the applicability of the common factors model to physical therapy and provide supportive evidence from evaluation and prognostic research on interventions for conditions seen in musculoskeletal physical therapy practice. The relevancy and consequences of applying the common factors model to physical therapy practice and research are discussed. The continued advance and evolution of the physical therapy profession requires creative and comprehensive analysis of all factors impacting clinical effectiveness. Additional research is needed to more clearly delineate the common factors that are operational in physical therapy practice and to measure their relative impact on clinical outcomes.