Modest, yet progressive: Effective therapists tend to rate therapeutic change less positively than their patients.

Empirical findings on self-serving biases amongst psychotherapists are inconsistent. We tested in a large naturalistic data set, if therapists are prone to illusory superiority when estimating their patients' outcome and whether this effect is buffered by therapists' effectiveness. A post-hoc analysis with  = 69 therapists, who treated  = 1080 patients, was conducted. Therapists' and patients' mean ratings for therapeutic improvement in the Clinical Global Impression Scale (CGI) were compared. Using a multilevel modelling approach, we further investigated the relation between the patient-therapist divergence in the CGI and actual therapeutic change in the Global Severity Index (GSI) of the Brief Symptom Inventory and in the Satisfaction With Life Scale (SWLS). Ratings in the CGI did not show significant differences between patients' and therapists' assessment of therapeutic change. Lower estimations by therapists, compared to patients' self-report, were associated with greater therapeutic change in GSI and SWLS. Therapists, on a whole, did not seem to be prone to illusory superiority when assessing therapeutic outcome. Contrary, the more modest the therapists' estimation of therapeutic outcome was, the greater the actual therapeutic change.