A study from Kings College London asked why the effectiveness of therapists varies. They examined the effect of experienced therapists using Cognitive Behavioural Therapy on people diagnosed with Chronic Fatigue Syndrome. They concluded:
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.
