We often hear the term “stress” associated with functional gastrointestinal (GI) disorders, such as irritable bowel syndrome (IBS). Many patients experience a worsening of symptoms during times of severely stressful life events. But what is stress? How often does it occur? How does our body respond to stress? This article explores the mechanisms that link stress and emotions to responses that have evolved to ensure survival and that, in the modern world, affect health – including gastrointestinal function.