Fourteen studies in total were included: 13 randomised controlled trials and one non-randomised controlled trial. Samples sizes are not reported for all studies, but at least 554 participants are included in the review.
Differences between the studies.
The studies varied with respect to patient populations, definitions of IBS, type of intervention, management of control groups, concurrent drug usage, and psychological assessment, as well as length of baseline period, duration of intervention, and length of follow-up.
Effectiveness of interventions.
Eight out of 14 studies (57%) reported that psychological therapy was significantly superior to control treatment in reducing the primary symptoms of IBS. Five studies failed to detect a significant effect of psychological therapy compared with a control group, although 3 of these did report significantly-reduced symptoms after psychological treatment, compared with baseline measures. However, one of these 3 also reported a deterioration in the condition of 29% of the treated patients. One study did not report whether psychological therapy was significant superior to control treatment.
Methodological quality of studies.
Only one study (a hypnotherapy trial) achieved the score for acceptable methodological quality, but this study was poorly generalisable due to sample selection.