Has cognitive behavioural therapy for psychosis been oversold?

Problems with the evidence

Promising results in early studies is one thing; demonstrating that a treatment is effective in large, well controlled trials is another. And it is here that cognitive behavioural therapy for schizophrenia has run into difficulties. There have been around nine moderately sized or large (35-257 participants in the cognitive therapy group), blind trials comparing cognitive behavioural therapy with usual treatment or a control psychological intervention (trials of psychotherapy are invariably carried out under single blind rather than double-blind conditions). Only two of these nine methodologically rigorous trials have had positive results on their primary outcomes of overall symptoms, positive symptoms, or relapse at the end of the treatment period,2 3 and in one of these the authors noted that the blinding became compromised as the trial went on.3

Notwithstanding the mixed signals from these and many other smaller or less rigorous studies, meta-analyses over the years have generally been supportive. The leading example here is unquestionably the meta-analysis, or rather series of meta-analyses, carried out for the 2009 National Institute for Health and Care Excellence’s schizophrenia guideline.4 On the basis of these, NICE concluded that cognitive therapy was effective in reducing rates of readmission to hospital and duration of admission. It was also judged to be effective in reducing overall symptom severity, both at the end of treatment and after up to …