Is it the symptom or the relation to it? Investigating potential mediators of change in acceptance and commitment therapy for psychosis.

Cognitive and behavioral interventions have been shown to be efficacious when used as an adjunct to pharmacotherapy for psychotic disorders. However, little previous research has investigated potential mediators of change in psychological treatments for psychosis. Acceptance and mindfulness-based therapies do not focus on directly reducing the psychotic symptoms themselves, but instead attempt to alter the patient's relationship to symptoms to decrease their negative impact. The current study examined this issue with data from a previously published randomized trial comparing brief treatment with Acceptance and Commitment Therapy (ACT) versus treatment as usual for hospitalized patients with psychotic symptoms (Gaudiano & Herbert, 2006a). Results showed that the believability of hallucinations at posttreatment statistically mediated the effect of treatment condition on hallucination-related distress. Hallucination frequency did not mediate outcome. The current study is a first step toward understanding the potential mechanisms of action in psychological treatments for psychosis.