When gut feelings turn into visceral pain: Placebo and nocebo mechanisms along the gut-brain axis

The experience of pain is shaped by a multitude of biological, psychological and social factors and is thus a complex psychological experience to be distinguished from nociception. Accordingly, the experience of pain can be modulated by psychological factors, and chronic pain conditions constitute biopsychosocial disorders. This is also true for visceral pain, which involves specific psychophysiological principles and neurobiological mechanisms, calling for an interdisciplinary approach at the interface of gastroenterology, psychology, pain research and the neurosciences. Based on the bidirectional connections between the gut and the brain and building on a biopsychosocial model, this review article describes psychological mechanisms that are important in the development, maintenance, and treatment of visceral pain. The focus is on positive and negative expectancy effects within the psychosocial treatment context. Treatment expectations can influence symptoms of the gut-brain axis, especially visceral pain, both positively and negatively. These phenomena, commonly known as placebo and nocebo effects, are mediated by doctor-patient communication, learning processes, stress, and fear. New interdisciplinary and translational research approaches from research on placebo and nocebo effects provide exciting insights into normal and pathological gut-brain interactions and may improve our knowledge about the etiology and pathophysiology of visceral hyperalgesia and interoceptive hypervigilance and provide important insights into new therapeutic approaches.