Common, Specific, and Treatment Fit Variables in Psychotherapy Outcome

The relative effects of and the relationship among specific interventions and nonspecific/relationship factors to improving treatment outcome have long been a source of debate among psychotherapists and outcome researchers. This study, the third in a series of analyses on a large, combined data set, tests the relative importance of two sets of "common factors" and two sets of "specific factors" that previous analyses have determined to be related to good treatment outcomes. Common factors included the therapeutic alliance and four patient factors. Specific factors included four dimensions of psychotherapy and four estimates of the fit between the characteristics of the patient and treatment factors. Patient, treatment, and treatment fit variables were assessed for their relative impact on both distal outcomes and proximal/alliance factors to obtain an estimate of the causal chain that exists among relationship and treatment factors. The results indicated that patient, therapy, and matching patterns were significantly associated both with the development of a therapeutic alliance and with outcome of treatment. Results suggest that dismantling treatment models and exploring how patient, treatment, relationship, and matching variables interact with one another and contribute to improvement, may enhance scientific understanding of treatment.