Therapist effects in routine psychotherapy practice: an account from chronic fatigue syndrome.

The effect of therapists in psychotherapy is a much debated topic, with a number of studies showing therapist variance being large while other studies show little or no variability in outcomes due to therapists. The aim of this study was to investigate therapist effects in a well-defined sample of patients and therapists from an outpatient service which specializes in providing cognitive behaviour therapy (CBT) for patients with chronic fatigue syndrome (CFS). Therapy was provided in a highly specialized clinical setting for CFS and was delivered by qualified CBT therapists with at least 2 years experience with this client group. Three hundred and seventy-four patients with CFS and 12 cognitive behavioural psychotherapists took part. Therapist effects on the primary outcomes of fatigue and disability were investigated with multilevel random effects models and variance component analysis. Different models were computed and compared. Results showed a reduction in fatigue and disability scores after therapy. Variance explained by therapists, when demographic covariates were accounted for, was 0% for fatigue and under 2% for disability. A number of important factors may have played a significant role in minimizing therapist effects in our study. These are: specialist setting, single centre, patients with the same primary diagnosis, therapists of the same orientation and training, shared environment and supervision. Future studies may stress the importance of these factors in the investigation of the therapist effect in psychotherapy.