BACKGROUND Previous studies have suggested that cognitive therapy is effective in modifying delusions.
AIMS To assess the effectiveness of cognitive therapy on patients seen in routine clinical work.
METHOD Eighteen patients with chronic delusions were treated using cognitive therapy, after the method of Chadwick and Lowe. A single-case multiple-baseline experimental design was used, including a control treatment. Each subject was used as their own control.
RESULTS Six patients reduced conviction in their delusions during cognitive therapy and not during the control treatment. Seven patients' conviction ratings did not change. Five patients showed a variable response. Degree of conviction did not fall to zero in any patient. All patients reported that the therapy had been helpful; six spontaneously mentioned changes in psychotic thinking.
CONCLUSIONS One-third of patients with chronic delusions whom we treated responded to delusion modification with a reduction in degree of belief. Change within therapy sessions predicted outcome, as did variation in the conviction during baseline. Cognitive therapy with delusions should aim at reducing distress as well as conviction.