Cognitive behavioural therapy (CBT) is an effective additional treatment for hallucinations and delusions in people with schizophrenia, say Swiss researchers.

Despite the proven effectiveness of antipsychotic drug treatments, a number of patients who have received such medications still experience "positive" symptoms, such as hallucinations, delusions and feelings of being controlled by outside forces, Dr G Zimmermann and colleagues, from the University of Lausanne, explain.

They add that, although a number of studies have suggested that CBT, which is designed to help people learn new patterns of thinking and behaviour, can improve positive symptoms in schizophrenia sufferers, the effectiveness of the technique is still unclear.

To investigate this issue further, the researchers analysed the results of 14 previous studies, published between 1990 and 2004 and involving more than 1400 participants, which focused on CBT as an additional treatment for people with schizophrenia.

They found that, compared with other additional treatments such as supportive therapy, as well as with no additional treatment, schizophrenia patients who received CBT showed significant improvements in positive symptoms.

Furthermore, this effect seemed to be particularly beneficial for patients suffering from an acute psychotic episode. Writing in the journal Schizophrenia Research, the investigators conclude: "CBT is a promising adjunctive [additional] treatment for positive symptoms in schizophrenia spectrum disorders."

However, they add that further research is needed to confirm their findings.