571 Type, Not Number, of Mental-Physical Comorbidities Increases the Severity of GI Symptoms in Patients With More Severe Irritable Bowel Syndrome

Abstract

BACKGROUND: While irritable bowel syndrome (IBS) is associated with significant mental and physical comorbidity, little is known about the day to day burden (e.g., quality of life [QOL], physical and mental functioning, distress, IBS symptoms) that comorbidity imposes. METHOD: 175 Rome III-diagnosed IBS patients (M age = 41 yrs, 78% Female, 91% Caucasian) completed psychiatric assessments (MINI International Neuropsychiatric Interview), a physical comorbidity checklist as well as the IBS Symptom Severity Scale, IBSQOL, Brief Symptom Inventory (distress, BSI), abdominal pain intensity scale, and the physical (PCS) and mental (MCS) functioning scales of the SF-12 as part of baseline assessment of an NIH clinical trial. RESULTS. IBS patients in this cohort reported an avg. of 5 diagnosed comorbidities (1 mental, 4 physical). Partial correlations indicated that subjects with more comorbidities reported worse QOL after adjusting for confounding variables. The number of physical comorbidities was more strongly associated with the physical aspects of QOL, while the number of mental comorbidities was more strongly correlated with mental aspects of QOL. The number of comorbidities was unrelated to either the intensity of abdominal pain or global severity of IBS symptoms. Multiple linear regression analyses indicated that comorbidity type was more consistently and strongly associated with illness burden indicators than simple disease counts after confounding variables were held constant. Of 10, 296 possible physicalmental comorbidity pairs, 6 of the 10 most frequent dyads involved a combination of conditions (generalized anxiety disorder, major depression, back pain, agoraphobia, tension headache, insomnia) that were consistently associated with illness (QOL, mental and physical functioning, distress) and symptom (IBS symptom severity, abdominal pain intensity) burden indicators. A comorbidity dyad with consistently large effect sizes was low back pain and major depression. For these patients, scores were expected to decrease by 22 points on the IBS QOL, 10.24 on the PCS, 11.76 on the MCS, and increase by 20.61 points on the BSI in comparison to patients who are not diagnosed with MDD and LBP. For the IBS-SSS, the regression coefficient was 89.67. This means that a patient diagnosed with MDD-LBP had IBS symptom severity scores on the IBS-SSS score that, on average, are 89.67 units higher than a patient undiagnosed with MDD and LBP. CONCLUSIONS. Physical-mental comorbidity in IBS is common, associated with increased distress and QOL impairment and, for patients with specific comorbidity profiles, more severe IBS symptoms. The type of reported comorbidities, rather than their number, may be a more useful way of understanding the full scope of their impact in more severely affected IBS patients. This study was funded by NIH Grant DK77738