OBJECTIVES: The goals of the study were the following: 1) to determine the frequency of psychiatric disorders and irritable bowel syndrome in patients with asthma and 2) to compare the frequency of these disorders in patients with asthma to their frequency in healthy controls. INTRODUCTION: Patients with asthma have a higher frequency of irritable bowel syndrome and psychiatric disorders. METHODS: We evaluated 101 patients with bronchial asthma and 67 healthy subjects. All subjects completed the brief version of the Bowel Symptoms Questionnaire and a structured clinical interview for DSM-IV axis disorders (SCID-I/CV). RESULTS: There were 37 cases of irritable bowel syndrome in the group of 101 stable asthma patients (36.6%) and 12 cases in the group of 67 healthy subjects (17.9%) (p = 0.009). Irritable bowel syndrome comorbidity was not related to the severity of asthma (p = 0.15). Regardless of the presence of irritable bowel syndrome, psychiatric disorders in asthma patients (52/97; 53.6%) were more common than in the control group (22/63, 34.9%) (p = 0.02). Although psychiatric disorders were more common in asthma patients with irritable bowel syndrome (21/35, 60%) than in those without irritable bowel syndrome (31/62, 50%), the difference was not significant (p = 0.34). In asthma patients with irritable bowel syndrome and psychiatric disorders, the percentage of forced expiratory volume in 1 s (FEV1) was lower than it was in those with no comorbidities (p = 0.02). CONCLUSIONS: Both irritable bowel syndrome and psychiatric disorders were more common in asthma patients than in healthy controls. Psychiatric disorders were more common in asthma patients with irritable bowel syndrome than in those without irritable bowel syndrome, although the differences failed to reach statistical significance. In asthma patients with IBS and psychiatric disorders, FEV1s were significantly lower than in other asthma patients. It is important for clinicians to accurately recognize that these comorbid conditions are associated with additive functional impairment.