Xi Chen at Aeon: Today, unlike in the 1990s, it is well established that conditions like IBS (irritable bowel syndrome), collectively known as disorders of gut-brain interaction (DGBIs), are real diseases that disrupt the communication between the nervous system of the brain and spine, and the nervous system of the intestines. First mentioned in the book The Irritable Gut (1979) by the gastroenterologist W Grant Thompson, the conditions were labelled ‘functional’ disorders – characterised not by structural damage to the hardware of the gut, but by a glitch in its ‘software’, in other words, its nervous system, charged with processing, receiving or relaying information coming in or going out. Software is not as easily observed as hardware, however, and much of academic medicine views the mind and the body as two separate and distinct entities, a viewpoint called mind-body dualism. Over time, and despite the more nuanced meaning intended by Thompson, the term ‘functional’ became associated exclusively with disorders of the mind.
This is part of the reason why there is still stigma against conditions like IBS, and why attempts to establish diagnostic criteria for IBS in particular suffered from vagueness. For centuries, there had been little agreement about how to even name the mysterious illness, and IBS went by names like mucous colitis, membranous enteritis, tubular diarrhoea, mucous colic, and myxoneurosis intestinalis. It was not until 2016 with the fourth iteration of what are called the Rome Criteria – a set of guidelines for IBS and other, similar diagnoses – that there has been a precise enough definition to dispel the label of functional disorders for good.
More here.