Changes in tolerance to rectal distension correlate with changes in psychological state in patients with severe irritable bowel syndrome.
OBJECTIVE: Reduced tolerance to rectal distension has been regarded as a biological marker for irritable bowel syndrome (IBS), but longitudinal studies are few. This study determined whether change in tolerance to rectal distension after psychological treatments was associated with: 1) change in abdominal pain; 2) change in psychological symptoms; 3) a reported history of sexual abuse. METHODS: Participants completed a visual analogue scale of abdominal pain, SCL-90 and Hamilton rating scale of depression; discomfort threshold to rectal distension was determined using a double random staircase protocol. These were measured at entry to a trial of psychotherapy or paroxetine (selective serotonin reuptake inhibitor antidepressant) and 3 months later (N = 52). Analysis of change scores were adjusted for treatment group and baseline values. RESULTS: Increased tolerance to distension after treatment was associated with reduction in depression (r = -0.37, p =.008) but not abdominal pain. Patients who reported prior sexual abuse showed greater increase in tolerance than the remainder (changes in volume threshold: -24.7 ml [SEM = 12.1] vs. 3.6 ml [SEM = 6.2], adjusted p =.045; changes in pressure threshold: -4.7 [SEM = 1.7] mm Hg vs. 0.96 [SEM=0.9], adjusted p =.005). Multiple regression indicated that reduction in depression score and a reported history of sexual abuse were independently associated with improved tolerance to distension. CONCLUSIONS: In patients with severe IBS, increased tolerance to rectal distension after psychological treatment is significantly associated with improved depression and reported sexual abuse. These results suggest that in some patients with severe IBS psychological rather than biological processes are primarily responsible for reduced tolerance to rectal distension.