Neuropsychiatric factors play important roles in IBS symptoms. Mood disorders such as bipolar disorder are prevalent in IBS. Antidepressants are used traditionally for management of IBS symptoms but antibipolar agents have not been studied. Aripiprazole an antibipolar agent was selected because of having the least anticholinergic side effects.

One hundred forty seven patients with diagnosis of IBS were included in the study. Randomly selected 74 patients were taken Nortriptyline 10mg/day and 73 Aripiprazole 5mg/day. Questionnaires of the Birmingham IBS Symptom for assessing the severity of IBS symptoms and the Mood Disorder Questionnaire for diagnosis of bipolar mood disorder were filled by all patients in the base time and then by 52 and 41 in month 1 and 40 and 28 in month 3, respectively. Two groups and subgroups of bipolar and nonbipolar disorder were compared in regard to severity of IBS during follow ups.

The decreases in mean scores were significant in each Aripiprazole and Nortriptyline groups during follow ups, but comparing them the changes were more in Aripiprazole compared to Nortriptyline groups, although the differences were not significant (p>0.05). The decrease in mean score were significant in each subgroups of bipolar and nonbipolar during follow ups, but comparing them the changes were significant only in bipolar subgroup of Aripiprazole group (p<0.05).

Aripiprazole has better efficacy than Nortriptyline for management of patients with IBS especially in subgroup of patients with bipolar disorder. Aripiprazole is attractive drug for substitution of Nortriptyline due to lower anticholinergic side effects in patients with IBS especially in predominant constipation or mixed bowel habits.