Impact of case formulation in cognitive behaviour therapy for psychosis.

Case formulation (CF) is the 'first principle' in cognitive behavior therapy (CBT), and the cornerstone of CT for psychosis. Experiment 1 (E1) assesses impact of CF in CBT for psychosis on perception of therapeutic relationship. Experiment 2 assesses the impact of CF on strength of delusional and self-evaluative beliefs (E2). Both E1 and E2 assess impact of CF on symptoms of anxiety and depression. CF had little or no impact on these variables. Descriptive data suggested there were other benefits for certain participants. Therapists' perception of the therapeutic relationship did improve following CF. Six clients found CF, at least in part, a negative experience.