In the population with FS, individuals with psychological disorders report more severe shoulder pain and functional limitation.[15] Psychological factors (such as emotional distress) might affect the intensity of pain and the persistence of disability.[43] Research has discovered that in individuals experiencing mood swings, the levels of tumor necrosis factor and pro-inflammatory cytokine IL-6 are elevated.[44] To some extent, these studies revealed the pathophysiological connection between GERD, mood swings, and FS. The gene discussed is IL6; the disease is gastroesophageal reflux disease.