title: Prediction of psychosis in youth at high clinical risk: a multisite longitudinal study in North America.
abstract: BACKGROUND
  Early detection and prospective evaluation of individuals who will develop schizophrenia or other psychotic disorders are critical to efforts to isolate mechanisms underlying psychosis onset and to the testing of preventive interventions, but existing risk prediction approaches have achieved only modest predictive accuracy.
  
  
  OBJECTIVE
  To determine the risk of conversion to psychosis and to evaluate a set of prediction algorithms maximizing positive predictive power in a clinical high-risk sample.
  
  
  METHODS
  Longitudinal study with a 2 1/2-year follow-up of 291 prospectively identified treatment-seeking patients meeting Structured Interview for Prodromal Syndromes criteria. The patients were recruited and underwent evaluation across 8 clinical research centers as part of the North American Prodrome Longitudinal Study.
  
  
  METHODS
  Time to conversion to a fully psychotic form of mental illness.
  
  
  RESULTS
  The risk of conversion to psychosis was 35%, with a decelerating rate of transition during the 2 1/2-year follow-up. Five features assessed at baseline contributed uniquely to the prediction of psychosis: a genetic risk for schizophrenia with recent deterioration in functioning, higher levels of unusual thought content, higher levels of suspicion/paranoia, greater social impairment, and a history of substance abuse. Prediction algorithms combining 2 or 3 of these variables resulted in dramatic increases in positive predictive power (ie, 68%-80%) compared with the prodromal criteria alone.
  
  
  CONCLUSIONS
  These findings demonstrate that prospective ascertainment of individuals at risk for psychosis is feasible, with a level of predictive accuracy comparable to that in other areas of preventive medicine. They provide a benchmark for the rate and shape of the psychosis risk function against which standardized preventive intervention programs can be compared.
authors.affiliation: Department of Psychology, University of California, Los Angeles, 1285 Franz Hall, Los Angeles, CA 90095. cannon@psych.ucla.edu.
authors.forename: Tyrone D
authors.initials: TD
authors.lastname: Cannon
authors.forename: Kristin
authors.initials: K
authors.lastname: Cadenhead
authors.forename: Barbara
authors.initials: B
authors.lastname: Cornblatt
authors.forename: Scott W
authors.initials: SW
authors.lastname: Woods
authors.forename: Jean
authors.initials: J
authors.lastname: Addington
authors.forename: Elaine
authors.initials: E
authors.lastname: Walker
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Seidman
authors.forename: Diana
authors.initials: D
authors.lastname: Perkins
authors.forename: Ming
authors.initials: M
authors.lastname: Tsuang
authors.forename: Thomas
authors.initials: T
authors.lastname: McGlashan
authors.forename: Robert
authors.initials: R
authors.lastname: Heinssen
mesh_terms: D000293:Adolescent; D000328:Adult; D000465:Algorithms; D014150:Antipsychotic Agents / Q000627:therapeutic use; D003071:Cognition; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D053208:Kaplan-Meier Estimate; D008137:Longitudinal Studies; D008297:Male; D010259:Paranoid Disorders; D011237:Predictive Value of Tests; D011379:Prognosis; D011618:Psychotic Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000235:genetics / Q000523:psychology*; D012307:Risk Factors; D012559:Schizophrenia / Q000453:epidemiology* / Q000235:genetics; D012919:Social Behavior; D019966:Substance-Related Disorders; D013577:Syndrome
chemical_list: D014150:Antipsychotic Agents