title: Specificity of cognitive deficits in bipolar disorder versus schizophrenia. A systematic review.
abstract: BACKGROUND
  More and more epidemiological, genetic and neuroimaging studies show similarities between bipolar disorder (BD) and schizophrenia (SZ). Cognitive functions are known to be highly impaired in SZ and are increasingly studied in BD. When both populations are compared, the conclusions appear to be contradictory. The purpose of this review is to help define the profile of cognitive deficits in BD and in SZ.
  
  
  METHODS
  A systematic review of the literature of neuropsychological studies comparing BD and SZ was made, beginning in January 1990 and ending in January 2005. Thirty-eight studies met the required quality criteria and were included in this review.
  
  
  RESULTS
  Bipolar patients exhibit extensive cognitive abnormalities with a pattern of deficits that is not unique to this disease. However, when compared to schizophrenic patients, bipolar patients demonstrate a lesser degree of deficits, particularly concerning premorbid and current intelligence quotient and perhaps attention, verbal memory and executive functions. When looking into effect sizes, there seem to be different profiles even in studies finding no significant differences.
  
  
  CONCLUSIONS
  The neuropsychological differences reported between both groups could be due to the presence of psychotic features, to environmental factors (stressful events, duration of the disease and number of hospitalisations) and could also be related to differences during the neurodevelopmental phase. Further studies should confirm whether these results are truly related to different neurobiological backgrounds.
authors.affiliation: Bipolar Disorders Program, Hospital Clinic, University of Barcelona, IDIBAPS, Barcelona, Spain.
authors.forename: Claire
authors.initials: C
authors.lastname: Daban
authors.forename: Anabel
authors.initials: A
authors.lastname: Martinez-Aran
authors.forename: Carla
authors.initials: C
authors.lastname: Torrent
authors.forename: Rafael
authors.initials: R
authors.lastname: Tabarés-Seisdedos
authors.forename: Vicent
authors.initials: V
authors.lastname: Balanzá-Martínez
authors.forename: Jose
authors.initials: J
authors.lastname: Salazar-Fraile
authors.forename: Gabriel
authors.initials: G
authors.lastname: Selva-Vera
authors.forename: Eduard
authors.initials: E
authors.lastname: Vieta
mesh_terms: D014150:Antipsychotic Agents / Q000627:therapeutic use; D001714:Bipolar Disorder / Q000188:drug therapy / Q000453:epidemiology*; D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D006304:Health Status; D006801:Humans; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000188:drug therapy / Q000453:epidemiology*; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D014150:Antipsychotic Agents