Relationship between intestinal mucosal inflammation and mental disorders in patients with irritable bowel syndrome

Objective To examine the relationship between inflammation and the comorbidity of mental disorders with irritable bowel syndrome (IBS) by comparing intestinal mucosa inflammatory biomarkers in patients with and without mental disorders.Methods A total of 43 consecutive IBS patients fulfilling the Rome Ⅲ criteria and 15 volunteers serving as controls without digestive symptoms were recruited and interviewed with Composite International Diagnostic Interview (CIDI) by the well-trained staff and thus classified as with or without mental disorders.All subjects underwent colonoscopy and biopsies were acquired from the mucosa of distal ileum and colon. CD3 + lymphocytes,mast cells,5-HT positive cells and (indoleamine 2,3-dioxygenase) IDO positive cells were identified immunohistologically in mucosa biopsies in volunteers (n =13 ),IBS patients without mental disorder (n =24 ) and IBS patients with mental disorder ( n =19).Results The incidence of mental disorders in IBS patients was significantly higher than that in the volunteers (19/43 vs 2/15,P =0.012),including 9 patients with anxiety disorders and 8 with mood disorders.( 1 ) The number of mast cells in IBS patients with mental disorder and that in IBS patients without mental disorder has no statistical significance ( ( 16.7 ± 3.6 )/HP vs ( 15.4 ± 3.1 )/HP in distal ileum,( 12.8 ±2.2)/HP vs ( 12.3 ± 2.5 )/HP in sigmoid,both P ＞ 0.05 ).Similar results were seen in 5-HT positive cells ( (3.7 ± 0.9 )/HP vs (3.4 ± 0.8 )/HP in distal ileum,(6.1 ± 1.8 )/HP vs(5.2 ± 1.8 )/HP in sigmoid,both P ＞ 0.05).In distal ileum,the number of CD3 + cells in IBS patients with mental disorder has no statistical significance with that in the IBS patients without mental disorder ( (62 ± 16)/HP vs(55 ±22)/HP,P ＞ 0.05 ).Similar results were seen in IDO positive cells (6 (2,8)/HP vs 2 (1,5)/HP,P ＞0.05 ).(2) The number of IDO positive cells from distal ileum in IBS patients with anxiety disorder was significantly higher than that in the IBS patients without mental disorder ( 6 ( 4,8 ) vs 2 ( 1,5 ),P =0.018).The number of mast cells from distal ileum in the IBS patients with mood disorder were significantlyhigher than that in those without mental disorders ( ( 18.3 ± 3.2)/HP vs ( 15.4 ± 3.1 )/HP,P =0.032).Conclusions Mental disorders in the IBS patients may be associated with intestinal mucosal inflammation.The activation of IDO may cause the comorbidity of IBS with anxiety disorder while the activation of mast cells probably leads to the comorbidity of IBS with mood disorder. Key words: Irritable bowel syndrome; Mental disorders; Comorbidity; Composite international diagnostic interview