Background: Little evidence exists for the effects of psychological treatment on voices even though it is clear that CBT does affect delusions and symptoms overall. This study tested whether a group based on cognitive behavioural principles could produce beneficial effects on hallucinations.
Aim: To test the effectiveness of group CBT on social functioning and severity of hallucinations.
Method: Participants were included if they had a diagnosis of schizophrenia and experienced distressing auditory hallucinations (rated on the PANSS). They were randomly allocated to group CBT (N = 45) or a control group who received treatment as usual (N = 40). The two main outcomes were social functioning as measured by the Social Behaviour Schedule and the severity of hallucinations as measured by the total score on the Hallucinations Scale of PSYRATS. Assessments were carried out at baseline, 10 weeks (post therapy) and 36 weeks (six months following therapy).
Results: Mixed random effects models revealed significant improvement in social functioning (effect size 0.63 six months after the end of therapy). There was no general effect of group CBT on the severity of hallucinations. However, there was a large cluster effect of therapy group on the severity of hallucinations such that they were reduced in some but not all of the therapy groups. Improvement in hallucinations was associated with receiving therapy early in the trial and having very experienced therapists (extensive CBT training which included expert supervision for a series of individual cases for at least a year following initial training).
Conclusion: Group CBT does improve social functioning but unless therapy is provided by experienced CBT therapists hallucinations are not reduced.