Researchers find CBT may not be plausible for positive or negative symptoms of schizophrenia
Schizophrenia is a group of severe brain disorders in which people interpret reality abnormally. Schizophrenia may result in some combination of hallucinations, delusions, and disordered thinking and behavior, according to the Mayo Clinic. Schizophrenia affects about 24 million people worldwide.
Cognitive-behavioral therapy (CBT) has been recommended as an evidence-based psychotherapy for the symptoms of schizophrenia. However, this view is based mainly on meta-analysis, whose findings can be influenced by failure to consider sources of bias.
For this new study researchers conducted a systematic review and meta-analysis of the effectiveness of CBT for schizophrenic symptoms that includes an examination of potential sources of bias.
Information was obtained from randomized trials providing end-of-study data on overall, positive and negative symptoms. The moderating effects of randomization, masking of outcome assessments, incompleteness of outcome data and use of a control intervention were examined. Publication bias was also investigated.
According to Keith Laws, BSc., PhD., C.Psychol., PGCertHE, AFBPsS, FHEA, Professor of Cognitive Neuropsychology and Head of Research in the School of Psychology at the University of Hertfordshire, "This study is a new meta-analysis of CBT in the treatment of schizophrenia. It is the most comprehensive study of its effect on symptoms ever undertaken -- covering fifty randomized controlled trials published over the last twenty years.
"We even translated papers from foreign languages, such as Chinese -- so our study covers everything worthy of
The results showed pooled effect sizes were –0.33 in 34 studies of overall symptoms, –0.25 in 33 studies of positive symptoms and –0.13 in 34 studies of negative symptoms. The key positive symptoms included delusions and hallucinations, which CBT was originally developed to target.
"Even this small effect disappeared when only studies where the assessors were blind were taken into account,” said Professor Laws.
Blind testing, where the investigators who make the assessments don't know which group of patients had received the therapy or not, is routinely used in trials of medical treatment but has not always been employed in studies of CBT for schizophrenia.
In their conclusion the researchers write “Cognitive-behavioral therapy has a therapeutic effect on schizophrenic symptoms in the ‘small’ range. This reduces further when sources of bias, particularly masking, are controlled for.”
This new research raises the question of whether CBT should continue to be recommended in clinical practice.
In closing Professor Laws comments "With this evidence, the current government policy which mandates this treatment for all patients with schizophrenia in England and Wales needs to be reconsidered.”
This study is published in The British Journal of Psychiatry.