title: Abnormal P300 in people with high risk of developing psychosis.
abstract: BACKGROUND
  Individuals with an "at-risk mental state" (or "prodromal" symptoms) have a 20-40% chance of developing psychosis; however it is difficult to predict which of them will become ill on the basis of their clinical symptoms alone. We examined whether neurophysiological markers could help to identify those who are particularly vulnerable.
  
  
  METHODS
  35 cases meeting PACE criteria for the at-risk mental state (ARMS) and 57 controls performed an auditory oddball task whilst their electroencephalogram was recorded. The latency and amplitude of the P300 and N100 waves were compared between groups using linear regression.
  
  
  RESULTS
  The P300 amplitude was significantly reduced in the ARMS group [8.6+/-6.4 microvolt] compared to controls [12.7+/-5.8 microvolt] (p<0.01). There were no group differences in P300 latency or in the amplitude and latency of the N100. Of the at-risk subjects that were followed up, seven (21%) developed psychosis.
  
  
  CONCLUSIONS
  Reduction in the amplitude of the P300 is associated with an increased vulnerability to psychosis. Neurophysiological and other biological markers may be of use to predict clinical outcomes in populations at high risk.
authors.affiliation: Institute of Psychiatry, Division of Psychological Medicine-Box 63, De Crespigny Park, London, SE5 8AF, UK. elvira.bramon@iop.kcl.ac.uk
authors.forename: Elvira
authors.initials: E
authors.lastname: Bramon
authors.forename: Madiha
authors.initials: M
authors.lastname: Shaikh
authors.forename: Matthew
authors.initials: M
authors.lastname: Broome
authors.forename: Julia
authors.initials: J
authors.lastname: Lappin
authors.forename: Daniel
authors.initials: D
authors.lastname: Bergé
authors.forename: Fern
authors.initials: F
authors.lastname: Day
authors.forename: James
authors.initials: J
authors.lastname: Woolley
authors.forename: Paul
authors.initials: P
authors.lastname: Tabraham
authors.forename: Mercè
authors.initials: M
authors.lastname: Madre
authors.forename: Louise
authors.initials: L
authors.lastname: Johns
authors.forename: Oliver
authors.initials: O
authors.lastname: Howes
authors.forename: Lucia
authors.initials: L
authors.lastname: Valmaggia
authors.forename: Víctor
authors.initials: V
authors.lastname: Pérez
authors.forename: Pak
authors.initials: P
authors.lastname: Sham
authors.forename: Robin M
authors.initials: RM
authors.lastname: Murray
authors.forename: Philip
authors.initials: P
authors.lastname: McGuire
mesh_terms: D000293:Adolescent; D001921:Brain / Q000503:physiopathology*; D004569:Electroencephalography; D018913:Event-Related Potentials, P300; D005072:Evoked Potentials, Auditory; D005260:Female; D006801:Humans; D008297:Male; D009483:Neuropsychological Tests; D011618:Psychotic Disorders / Q000503:physiopathology*; D012307:Risk Factors