70 60 50 40 30 20 10 0 O C E A N Male Five personality dimensions in patients with IBS 10 15 Female 4 Figure 1 Scores of personality factors in irritable bowel syndrome patients deﬁned by gender. Abbreviations: O, openness to experience; C, conscientiousness; E, extraversion; A, agreeableness; N, Neuroticism. extraversion (26.51 vs 25.65 in male, p = 0.014) compared to men (shown in Figure 1). Discussion The present manuscript, as a part of a larger study was designed to investigate the personality characteristics of nonpsychiatric IBS patients. Emotional states and personality traits may affect the physiology of the gut (Guthrie et al 1991), play a part in how symptoms are experienced and interpreted and can inﬂuence treatment (Bennet et al 1998; Wooda 1999). This can be obliging while considering the management strategy to achieve a better outcome in IBS patients which the prevalence has been reported to be 18.4% in our population (Drossman et al 1999). The ﬁve-factor model provides a dimensional account of the structure of normal personality traits, dividing personality into the ﬁve broad dimensions. Neuroticism and aggres- sion are reported to be higher in patients with functional gastrointestinal disease without psychiatric comorbidity and personality traits are believed to inﬂuence pain reports (Tanum and Malt 2001). A low level of neuroticism and little concealed aggressiveness is reported to predict treatment Neuropsychiatric Disease and Treatment 2008:4(5) outcome with the antidepressants in nonpsychiatrics, which was most prominent in women. These personality dimensions were better predictors of outcome compared to serotonergic sensitivity (Fock et al 2001). Differences between male and female patients with IBS were noticed elsewhere. Signiﬁcant differences found in the trait neuroticism, extraversion, and conscientiousness was consistent with other studies that suggest women consistently score higher than men on self-reported trait anxiety (Talley et al 1990; Tran et al 2006). The data for nonpsychiatric individuals drawn from a pool prepared for standardization of the Iranian version of NEO PI-R are among limitations of the present study. In the current study IBS patients scored higher in neuroticism and conscientiousness and scored lower in agreeableness and openness. Neuroticism is a person- ality trait characterized by overstated reactivity to physi- ological changes and unstable emotions. It is also related to emotional regulation, motivation, and interpersonal skills. Centrally targeted medications, such as anxiolytics and low-dose tricyclic antidepressants, which involve inhibitory effects on the sensitivity of the emotional motor system 961