Functional disorders of the digestive system, such as irritable bowel syndrome, are often associated with affective disorders, such as depression, anxiety, panic, and posttraumatic stress disorder (PTSD). Some of these associations are observed not only in clinical populations, but also in population-based samples, suggesting a relationship with pathophysiologic mechanisms underlying both gastrointestinal (GI) dysfunction and certain affective disorders. Sustained and acute life-threatening stressors play an important role in the onset and modulation of GI symptoms as well as in the development of affective disorders and PTSD. A neurobiological model is proposed that attempts to explain the development of visceral hypersensitivity, the neuroendocrine and autonomic dysfunction characteristic of functional GI disorders, as well as the overlap with affective disorders.