A 30-year-old woman has anxiety about episodes of abdominal pain that have alternated with diarrhea and constipation over the past year. She often has these episodes when she is stressed or tired. Physical examination and laboratory studies are within normal limits during these episodes. Which of the following is the most likely diagnosis?
B. Generalized anxiety disorder
D. Irritable bowel syndrome
E. Major depressive disorder
F. Somatization disorder
Correct answer : D. Irritable bowel syndrome