The body signals the brain when the stomach is empty, which sends the body messages that it needs food. However, the digestive system has its own brain, called the enteric nervous system, located within the walls of the tubular-shaped digestive tract. Unlike the main brain, the ENS only controls digestive functions. Contrary to previously held theories, researchers now believe that gastrointestinal issues such as irritable bowel syndrome and constipation cause messages to travel to the ENS, triggering mood changes and resulting in anxiety or depression.

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