The Impact of Mood and Somatization on Quality-of-life in Irritable Bowel Syndrome (IBS)

Abstract

Purpose: Irritable bowel syndrome (IBS) exerts a negative influence on quality-of-life (QOL) in affected individuals. IBS patients are known to have impairments in QOL comparable to individuals with other chronic GI illnesses, including inflammatory bowel disease and chronic liver disease (El-Serag et al., Aliment Pharmacol Ther 2002). In up to half of IBS patients, co-morbid psychiatric illness (e.g. depression, anxiety, somatization) can be detected; these psychiatric conditions, too, are known to negatively affect QOL. We sought to determine whether the presence of psychiatric co-morbidity further influences QOL while controlling for the effect of bowel symptoms alone in IBS patients. Methods: Consecutive patients presenting for care in a tertiary outpatient GI setting with a diagnosis IBS were recruited to complete several instruments, including: Rome III Research Diagnostic Questions, mood measures (Beck Depression and Anxiety Inventories), the SF-36 health-related QOL index, and the PHQ-15 somatization scale. Bowel symptom severity was assessed using a 10-cm VAS measure, and the number of symptomatic days over the preceding two weeks were recorded. Multivariate linear regression analysis was conducted to assess the independent contribution of demographics, bowel symptoms, and psychiatric measures on QOL. Results: 279 IBS subjects (49.5±14.7 yrs, 219 female) were recruited over a 52-month period. Mean bowel severity score was 6.9±2.6 on VAS scales, with 9.1±4.2 symptomatic days over the past 2 weeks. Mean score for the total SF-36 was 50.9±23.4. Mean BDI and BAI scores were 10.5±8.8 and 12.8±9.6, respectively, corresponding to 79 (28.3%) subjects with depression (BDI ≥14) and 94 (33.7%) with anxiety (BAI ≥16). Mean PHQ-15 scores were 12.8± 5.8, with 128 (25.5%) meeting criteria for ‘high somatization’. In the 146 (52.3%) subjects with ≥ 1 psychiatric comorbidity, poor QOL was noted with significantly lower mean SF-36 scores compared to the remainder (38.3±19.8 vs. 64.7±19.0, p<0.001). In multivariate analysis, poorer QOL was independently predicted by depression (B=-0.45, p<0.001) and somatization (B=-0.30, p<0.001) scores, older age (B=-0.19, p<0.001), and trended toward significance with bowel symptom severity (B=0.-10, p=0.11), but was not related to bowel symptom frequency (B=0.07, p=0.30), gender (B=0.01, p=0.76), or anxiety rating (B=-0.08, p=0.28). Conclusion: Co-existent mood disorders and somatization are common in IBS, and negatively influence QOL independent of bowel symptom severity and frequency. In addition to bowel symptoms, psychiatric comorbidity, particularly depression and somatization, may be equally important therapeutic targets in optimizing the well-being of IBS patients.