Functional heartburn = is defined as the presence of heartburn (retrosternal burning or pain) that is unrelated to oesophageal acid exposure and is not caused by gastro-oesophageal reflux.
Functional dyspepsia = is characterised by predominant epigastric pain or burning (epigastric pain syndrome), or early satiety or discomfort after meals (postprandial distress syndrome).
To diagnose functional heartburn or functional dyspepsia, symptoms must have been present for 6 months and investigated appropriately to exclude structural and metabolic causes