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Selective Processing of Gastrointestinal Symptom-related Stimuli in Irritable Bowel Syndrome

From the Department of Gastroenterology, East Surrey Hospital, Redhill, United Kingdom (M.A.); Academic Unit of Psychiatry, Cotham House, Bristol, United Kingdom (J.P.P.); Clinical Science at South Bristol, Bristol Royal Infirmary, Bristol, United Kingdom (C.S.J.P.); Department of Experimental Psychology, University of Bristol, Bristol, United Kingdom (M.R.M.).

Address correspondence and reprint requests to M. R. Munafò, PhD, Department of Experimental Psychology, University of Bristol, 8 Woodland Road, Bristol OX2 6HE, United Kingdom. E-mail: marcus.munafo{at}bristol.ac.uk

Objectives: We sought to determine whether irritable bowel syndrome (IBS) was associated with attentional bias toward symptom-related cues in IBS patients versus healthy controls, using a modified Stroop task to measure selective processing of gastrointestinal symptom-related cues.

Methods: Fifteen patients with a clinical diagnosis of IBS and 15 healthy controls were recruited into the study. All participants attended a single testing session, during which they completed a modified Stroop task using gastrointestinal symptom-related and neutral control words.

Results: Results indicated a significant main effect of word type (p = .013), with slower color-naming times for IBS-related compared with neutral words, and a significant main effect of exposure (p = .001), with slower color-naming times in the unmasked condition compared with the masked condition. The group x word type x exposure interaction was significant (p = .048). A series of post hoc tests indicated that among patients there was significant interference of symptom-related words in the masked condition but not in the unmasked condition, whereas among controls, the reverse was true.

Conclusions: These results indicate that IBS patients selectively process gastrointestinal symptom-related words compared with neutral words when they are presented subliminally but not when they are presented supraliminally. In contrast, healthy controls demonstrate the opposite pattern. Implications for the cognitive mechanisms in IBS, and future research directions, are discussed.

Key Words: attentional bias • irritable bowel syndrome • modified Stroop

Abbreviations: IBS = irritable bowel syndrome; RT = reaction time; CBT = cognitive behavioral therapy.