title: Pain insensitivity in schizophrenia: trait or state marker?
abstract: OBJECTIVE
  As early as the turn of the 20th century, clinicians observed patients with schizophrenia failing to respond to the pain of a myocardial infarction, ruptured appendix, or perforated bowel. Although this pain insensitivity in individuals with psychosis has been described in the literature for many years, the phenomenon is still poorly understood. We therefore reviewed the literature for findings concerning whether pain insensitivity in schizophrenia represents a state or a trait marker.
  
  
  METHODS
  A comprehensive Medline search of the literature on pain insensitivity in subjects with schizophrenia was conducted.
  
  
  RESULTS
  While the literature contains anecdotal observations, case reports, and a few rigorous clinical studies concerning patients with schizophrenia being relatively indifferent to pain, there is a dearth of empirical, well-controlled studies in this area. Although early studies that examined the response of individuals with schizophrenia to thermal or electrical pain were constrained by a variety of methodological confounders, studies on this topic suggest that the higher pain thresholds observed in schizophrenia are best explained by a complex, multifactorial model. Most intriguing are the results of one recent study that found pain insensitivity in family members of persons with schizophrenia, suggesting that this phenomenon may be a trait or endophenotype rather than being due to a psychotic state.
  
  
  CONCLUSIONS
  Pain insensitivity in individuals with schizophrenia, which is associated with increased morbidity and mortality, is poorly understood. It is possible that pain insensitivity might serve as a prodromal predictor of susceptibility for schizophrenia. Future studies are needed to further clarify the neurobiology, pathophysiology, and practical clinical implications of this phenomenon.
authors.affiliation: University of Cincinnati College of Medicine and Cincinnati Children's Hospital Medical Center, 45267, USA.
authors.forename: Manpreet K
authors.initials: MK
authors.lastname: Singh
authors.forename: Lisa L
authors.initials: LL
authors.lastname: Giles
authors.forename: Henry A
authors.initials: HA
authors.lastname: Nasrallah
mesh_terms: D000208:Acute Disease; D006801:Humans; D010146:Pain / Q000175:diagnosis* / Q000453:epidemiology*; D010147:Pain Measurement; D015995:Prevalence; D011618:Psychotic Disorders / Q000453:epidemiology; D012559:Schizophrenia / Q000453:epidemiology*; D012720:Severity of Illness Index