title: Neurophysiological biomarkers support bipolar-spectrum disorders within psychosis cluster.
abstract: BACKGROUND
  Mismatch negativity (MMN) and P3a are event-related potentials that index deviance detection and the orienting response, respectively. We have previously shown that the MMN/P3a complex is impaired in patients with schizophrenia and affective spectrum psychoses, which suggests that it may index a common pathophysiology and argues against the purported specificity in schizophrenia. Further research is warranted to determine whether patients with bipolar-spectrum disorders show similar impairments in these biomarkers.
  
  
  METHODS
  We assessed patients aged 15-30 years with early schizophrenia-spectrum disorders (schizophrenia, schizoaffective disorder, schizophreniform disorder), early bipolar-spectrum disorders (bipolar I or II, with and without psychotic features) and healthy, matched controls. We acquired MMN/P3a amplitudes during a 2-tone, auditory paradigm with 8% duration deviants. Clinical, psychosocial and neuro psychological assessments were also undertaken.
  
  
  RESULTS
  We included 20 patients with schizophrenia-spectrum disorders, 20 with bipolar-spectrum disorders and 20 controls in our study. Both patient groups showed significantly reduced frontocentral MMN and central P3a amplitudes. The schizophrenia-spectrum group had additional impairments in left temporal MMN and frontal P3a. Both patient groups performed worse than controls across psychosocial and clinical measures; however, only the schizophrenia-spectrum group performed significantly worse than controls for cognitive measures. Correlational analyses between patient groups revealed associations between frontocentral or left temporal MMN and psychiatric symptomatology or quality of life measures.
  
  
  CONCLUSIONS
  Limitations to our study include the modest sample size and the lack of control with regards to the effects of other (i.e., nonantipsychotic) psychotropic medications.
  
  
  CONCLUSIONS
  Compared with patients in early stages of schizophrenia-spectrum disorders, those in the early stages of bipolar-spectrum disorders are similarly impaired in established biomarkers for schizophrenia. These findings support a shared diathesis model for psychotic and bipolar disorders. Furthermore, MMN/P3a may be a biomarker for a broader pathophysiology that overlaps traditional diagnostic clusters.
authors.affiliation: Clinical Research Unit, Brain & Mind Research Institute, University of Sydney, Sydney, Australia. manreena.kaur@sydney.edu.au
authors.forename: Manreena
authors.initials: M
authors.lastname: Kaur
authors.forename: Robert A
authors.initials: RA
authors.lastname: Battisti
authors.forename: Jim
authors.initials: J
authors.lastname: Lagopoulos
authors.forename: Philip B
authors.initials: PB
authors.lastname: Ward
authors.forename: Ian B
authors.initials: IB
authors.lastname: Hickie
authors.forename: Daniel F
authors.initials: DF
authors.lastname: Hermens
mesh_terms: D000161:Acoustic Stimulation / Q000379:methods / Q000523:psychology; D000293:Adolescent; D000328:Adult; D015415:Biomarkers; D001714:Bipolar Disorder / Q000150:complications / Q000503:physiopathology*; D016022:Case-Control Studies; D002540:Cerebral Cortex / Q000503:physiopathology*; D003072:Cognition Disorders / Q000150:complications / Q000503:physiopathology; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests / Q000706:statistics & numerical data; D011569:Psychiatric Status Rating Scales / Q000706:statistics & numerical data; D011618:Psychotic Disorders / Q000150:complications / Q000503:physiopathology*; D011788:Quality of Life / Q000523:psychology; D012559:Schizophrenia / Q000150:complications / Q000503:physiopathology; D012565:Schizophrenic Psychology
chemical_list: D015415:Biomarkers