Kahrilas et al. described psychogenic factors as an alternative explanation for PPI-refractory symptoms: hyperalgesia, allodynia, hypervigilance, and increased anxiety. Anxiety and depression were found to increase GERD-related symptoms in a population-based study. Patients with a poor reflux-symptom correlation reportedly exhibit a high level of anxiety compared with patients exhibiting good reflux-symptom correlation. In addition, it has been shown that increased levels of anxiety were associated with more severe retrosternal pain and retrosternal burning in GERD patients along with increased levels of anxiety and depression.