Almost 90 years of common factors: Are they still useful in research and practice?

Abstract

Traditionally, psychotherapy distinguishes between "common factors" and "specific mechanisms." Common factors can be defined as "unrecognized factors in any therapeutic situation-factors that may be even more important than those being purposely employed." Specific mechanisms, by contrast, are deliberately targeted by given therapeutic approaches as the primary drivers of change. This distinction is based on the implicit assumption that each therapeutic ingredient fits exclusively into one of these categories. In this viewpoint, the author argues that the common versus specific dichotomy is both arbitrary and potentially detrimental. It risks preventing clinicians from using specific techniques to target some of the most effective therapeutic mechanisms identified in research. The trait-like and state-like theoretical framework has demonstrated that the term "common factor" is less useful as a fixed attribute and it is more productive to consider it as one potential role that mechanisms may play, alongside their ability to function as specific mechanisms targeted directly to drive state-like therapeutic change. This shift parallels the evolution from viewing individual characteristics as pure traits (e.g., personality traits) or states (e.g., emotional states) to recognizing them as coexisting dimensions of the same construct: Personality traits can display state-like fluctuations across time and contexts, while emotional states may follow stable trait-like patterns over time. (PsycInfo Database Record (c) 2025 APA, all rights reserved).