There is still considerable disagreement as to what makes psychotherapy effective. The controversy about the comparative efficacy of different psychotherapy approaches has generated two different major perspectives on the active ingredients in psychotherapy: the specific ingredients model and the common factors model. However, conceptual analyses and empirical data rather suggest a synergistic view of specific and common factors.

The study aims at contributing to a clearer conceptualization of common factors by analyzing their associations with treatment techniques.

A comprehensive literature search was performed to identify the common factors discussed in psychotherapy research. Psychotherapy experts then rated the degree of associations between these common factors and a set of techniques in a web-based survey. A factor analysis was performed to analyze the dimensional structure of common factors, which underlies the rated associations between common factors and techniques. In addition, the techniques associated with the different dimensions of common factors were analyzed by regression analysis.

The factor analysis reveals that the variety of common factors can be described by a four-dimensional structure: common factors related to 1) cognitive processing, 2) emotional processing, 3) coping and 4) common factors fostering therapeutic alliance or therapy motivation. These dimensions are characterized by specific patterns of associated techniques.

Common factors have great potential to contribute to a clarification of the change mechanisms induced by psychotherapy. However, the construct suffers from major conceptual problems. The presented classification represents a first step towards a conceptual clarification of common factors in psychotherapy.