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Psychiatry has enjoyed a particularly interesting relationship with the gastrointestinal (GI) illnesses since the brain–gut relationship was considered one of the core examples of how psychological stress could influence autonomic processes,1 until increasing understanding regarding the pathophysiology underlying stomach and duodenal disorders diminished interest in this relationship. Still, it remains a fact that the brain and digestive tract are intimately connected and more recent—and more modest—research reveals strong evidence for direct and indirect influences of one on the other. Considering that depression can be a consequence of both physiological and psychological stress, it should be no surprise that depressive disorders very commonly co-occur with GI disorders. This chapter will consider several examples of the complex relationship between depressive disorders and GI disorders, including peptic ulcer disease, irritable bowel syndrome (IBS), inflammatory bowel disease (IBD), and various diseases of the liver.
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Peptic ulcers are erosions of the GI lining that extend through the mucosa of the GI lumen. Ulcers can occur anywhere along the alimentary tract; however, they are most likely to occur in the stomach or in the proximal bulb of the duodenum: the “peptic” regions, so called because these are the areas that have the most contact with the corrosive digestive juices gastric acid and pepsin. This is why gastric and duodenal ulcers are collectively referred to as “peptic ulcers,” and as they are pathologically similar, they are usually considered together. The peptic lumen has adapted to protect against the effects of constant contact with acids and proteolytic enzymes through adaptations of the mucosal lining and its protective mucus layer; ulcers only occur when some pathological process disrupts this normal protection. Considered a disorder of the modern age,2 the incidence of peptic ulcer disease rose dramatically in the 19th century, peaked in the first half of the 20th century, and then began to decline after the 1950s with advances in diagnosis and treatment. Despite these advances, they remain common, with an estimated prevalence of about 8% in the United States and an estimated cost of more than 3 billion dollars per year. The relationship of peptic ulcers to psychiatry is particularly interesting: thought to be a classic “psychosomatic” disease for much of the 20th century, research on the psychological aspect of ulcers was largely abandoned after it was discovered that the great majority were infectious in etiology. However, this understanding is incomplete and there is some renewed interest in the role of psychological stress and psychiatric disease, both as risk factors, perpetuating factors, and as possible complications of this disease.
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Epidemiological studies support an association between depression and peptic ulcer disease (Fig. 13-1, Box 13-1). A large epidemiological study in the United States demonstrated the association between mood and anxiety disorders and peptic ulcer disease: for the mood disorders, this ...