Improving cognitive treatments for delusions.

A clear challenge for schizophrenia research is to improve markedly the efficacy of psychological treatments for delusional beliefs. Effect sizes for the first generation of cognitive approaches are weak to moderate. These therapies now lag behind the transformation over the past ten years in understanding the causes of delusions. This paper advocates an interventionist-causal model approach: to focus on one putative causal factor at a time, show that an intervention can change it, and examine the subsequent effects on the delusional beliefs. A number of new studies that illustrate this approach with patients with schizophrenia spectrum disorders who have not responded to previous treatment are reviewed. These early stage studies show great promise in terms of efficacy, although remain to be subjected to methodologically rigorous evaluation. The advantages and difficulties of the interventionist approach applied to psychosis are considered, and future studies are highlighted. The importance for clinical services of cognitive approaches to psychosis will increase further if the theoretical advances can be translated into treatment.