Practice Innovations, Vol 11(1), Mar 2026, 42-53; doi:10.1037/pri0000287
Several models have attempted to explain the contribution of various therapeutic factors to psychotherapy outcomes. Norcross and Lambert’s (2011) frequently cited model suggests that 30% of the contribution is made by the client, 12% by the relationship, 8% by the treatment, 7% by the therapist, and 3% by other factors and 40% is unexplained. However, these models primarily consider the researcher perspective regarding the causes of change in psychotherapy. The purpose of the present study was to identify therapist and client perspectives of the factors that lead to change in psychotherapy. Participants were a nationwide sample of 149 practicing therapists and 232 current or former psychotherapy clients recruited from mental health clinics. Therapists and clients were told that 40% of the psychotherapy outcome variance is unexplained and 3% is explained by other factors. They were then asked to provide their own estimates for the contribution of the client, the relationship, the treatment, and the therapist to psychotherapy outcomes. Overall, the client and therapist samples differed in their views of the factors that lead to change in psychotherapy when compared with the researcher view. Clients viewed their own contribution as the most important factor (although estimating their contribution to be much smaller than estimated by researchers), while therapists rated the therapeutic relationship the highest. These findings highlight the importance of listening to client and therapist perspectives to better understand psychotherapy outcomes. Future research should seek to bridge the gap between theory and practice by engaging all stakeholders in psychotherapy research. (PsycInfo Database Record (c) 2026 APA, all rights reserved)