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How the Mind-Gut Connection Affects Your Health

The 'second brain' in your stomach can cause or relieve illness and stress. Here's how it works.

By Lawrence Friedman, M.D. | June 24, 2013
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Lawrence Friedman, M.D., is a professor of medicine at Harvard Medical School and Tufts University School of Medicine, chair of the department of medicine at Newton-Wellesley Hospital and assistant chief of medicine at Massachusetts General Hospital. He is the medical editor of The Sensitive Gut, a special health report from Harvard Medical School.




Have you ever had a "gut-wrenching" experience? Do stressful situations put "butterflies" in your stomach? Did you ever make a decision on "gut instinct"? We use such expressions to describe emotional situations precisely because our gastrointestinal tract is sensitive to our emotions. Anger, anxiety, sadness, elation – all of these emotions, and many others, trigger a physical reaction in the gut.
 
Early researchers relied on some remarkable observations to learn how our digestive tract responds to emotions. In 1833, U.S. Army surgeon William Beaumont treated Alexis St. Martin, a French-Canadian traveler who had been shot in the stomach. The wound left an opening to the skin that let Beaumont observe the pumping, to-and-fro motion of the stomach and also see what happened when his patient expressed different emotions. For example, St. Martin's stomach produced less acid when he was fearful, angry or impatient.

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We now know that the brain has a direct line to the stomach. Just the thought of eating can release digestive juices long before we swallow our food. And the connection works both ways: a distressed gut can be as much the cause of anxiety, stress and depression as their product.

The brain and the gastrointestinal system are so intimately connected that they should be viewed as one system, not two. When the gut acts up for no obvious physical or infectious cause, trying to heal it without considering the impact of stress and emotion is like trying to improve an employee's performance without considering his or her manager and work environment.
 
Our Second Brain
 
The gut is controlled by the enteric nervous system, sometimes called the second brain. This complex system of about 100 million nerves oversees every aspect of digestion and communicates with the central nervous system through pathways of nerves. It arises from the same tissues as the central nervous system during fetal development and has many structural and chemical counterparts in the cranial brain. The enteric nervous system also uses many of the same neurotransmitters, or chemical messengers, as the central nervous system.
 
As food makes its 30-foot journey through the digestive tract, the enteric nervous system participates in a rich dialogue with the brain via the autonomic nervous system, which controls the body's vital functions. This two-way communication explains why you stop eating when you're full – sensory neurons in your gut tell your brain that your stomach is distended. It's also why anxiety over an afternoon doctor's appointment could ruin your appetite for breakfast. In the latter case, stress activates your "fight or flight" response, which inhibits gastrointestinal secretion and reduces blood flow to the gut.
 
No one who has felt nauseated before a presentation or performance needs to be told how closely the gut and brain interact. That doesn't mean every functional gastrointestinal (GI) illness is "all in your head." But psychology can combine with physical factors to cause symptoms. Stress or depression can affect the movement and contractions of the GI tract, cause inflammation or make you more susceptible to infection.
 
Given these connections, it's no surprise that a review of 13 separate studies showed that people with functional gastrointestinal illness who tried psychologically-based approaches found greater relief from their symptoms than those who received conventional treatment alone.
 
How We Treat the Gut

For many people, gastrointestinal symptoms respond well to changes in diet or medication. When symptoms don't improve — or when there are associated so-called "alarm" symptoms such as weight loss, fever or blood in the stool — doctors may perform diagnostic tests to rule out a physical abnormality, infection or cancer. (In some cases, symptoms improve as soon as cancer has been ruled out – another example of how emotion affects the gut.) But when there is no evidence of such causes and symptom-specific treatments are not enough, it is more likely that the patient is experiencing some sort of psychological distress.
 
Some people are reluctant to accept the role of psychosocial factors in their illnesses. But emotions cause genuine chemical and physical responses in the body. When symptoms arise from stressful circumstances, psychological treatments can be beneficial. Behavioral therapy and stress-reduction techniques do not directly reduce pain or improve symptoms in the same way as drugs, but they can deliver similar results by reducing anxiety, encouraging healthy behaviors or just helping individuals cope with discomfort.
 
Cognitive Behavioral Therapy Working with a therapist can reframe negative thinking and behaviors that affect your symptoms and quality of life. The goal of cognitive behavior therapy is to change counterproductive thoughts and actions and learn new coping skills. This may be accomplished through a number of means, including changing negative thought patterns, learning stress management and relaxation exercises, modeling healthy behaviors and role playing.
 
Therapy can reduce the stress of dealing with a disorder so that it is no longer the focal point of your life. As stress decreases, symptoms often improve, reducing anxiety even further. In one study of people with irritable bowel syndrome, 70 percent reported less pain, bloating and diarrhea after 12 weeks of cognitive behavioral therapy.
 
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Most behavioral therapists are not specifically trained in treating gastrointestinal disorders. More likely, a therapist would teach you general techniques you can apply to your situation. You can find a licensed cognitive behavioral therapist in your area through your doctor, health plan or the Academy of Cognitive Therapy.
 
Relaxation Therapy This approach helps people to be more relaxed when confronted by pain or stress. Therapists use progressive muscle relaxation, mental imaging, music and even aromas to induce a natural state of relaxation. During and after therapy, thoughts begin to flow slowly and naturally, muscle tension diminishes and breathing slows and becomes deeper and more regular. The result: The body can relax and digest.
 
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One small study found that patients with irritable bowel syndrome who practiced a form of relaxation therapy called the Relaxation Response enjoyed significant short- and long-term reductions in pain, bloating, diarrhea and flatulence. Other relaxation techniques include yoga, meditation, hypnosis and biofeedback.
 
Antidepressants It's important that the small minority of people who have severe, debilitating gastrointestinal symptoms be evaluated for anxiety and depression. Such individuals tend to have a high frequency of these mood disorders or a history of loss, abuse or trauma.
 
When anxiety or depression appears to be a factor in a gastrointestinal disorder, an antidepressant may help, even in the absence of a diagnosis of depression or anxiety. These medications are most often prescribed to alleviate depression and anxiety, but in lower doses they can also relieve pain. An analysis of 12 studies of men and women with irritable bowel syndrome and functional dyspepsia showed that those who took an antidepressant had greater improvement in abdominal pain scores than with those who took a placebo. Antidepressants also can benefit the rhythmic contractions of the gut which are necessary for healthy digestion.
 
Guts on the Field Comes From the Gut
 
Have you ever noticed that you feel less pain when you're doing something that requires all your attention, like competing in a race or other athletic competition? That's because pain is not a one-way street. Your brain can inhibit pain signals from the gut.
 
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Experts call it the "gate control" theory. Receptors in your intestines known as afferent receptors send pain signals to the brain. But certain centers in the spinal cord known as "pain gates" can regulate that pain. Fibers in these centers can allow a pain signal to proceed to the brain or "close the gate" when they receive an inhibiting signal from the brain. Your brain does this naturally when you are doing something that requires deep concentration, such as playing a sport intensely. Antidepressant medications can also help close the gate by blocking or inhibiting the pain signal to the brain.

Knowing how your emotions may be affecting your gut, and vice versa, can help you address your next gut-wrenching episode or gastrointestinal ailment more quickly and effectively.
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