Although the exact cause of GERD is uncertain, it's believed to be a result of different physiological and anatomical factors that inhibit the reflux of gastric juice traveling from the stomach to the esophagus. Such factors include abnormalities in the lower esophageal sphincter (LES) functioning and hiatal hernias. The LES of people who suffer from GERD tends to slow down and not play as active a role as it should during the time that the rest of the esophagus is doing its job.

A hiatal hernia comes about when the lower esophageal sphincter and upper division of the stomach travel above the diaphragm in where the esophagus routes from the chest into the abdomen. Hiatal hernias develop at the opening of the diaphragm where the esophagus connects to the stomach. The condition becomes symptomatic when the diaphragm fails to block food and acid from receding into the esophagus.