Prediction of psychosis in youth at high clinical risk: a multisite longitudinal study in North America.
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.
Cannon
Tyrone D
TD
Department of Psychology, University of California, Los Angeles, 1285 Franz Hall, Los Angeles, CA 90095. cannon@psych.ucla.edu.
Cadenhead
Kristin
K
Cornblatt
Barbara
B
Woods
Scott W
SW
Addington
Jean
J
Walker
Elaine
E
Seidman
Larry J
LJ
Perkins
Diana
D
Tsuang
Ming
M
McGlashan
Thomas
T
Heinssen
Robert
R
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
D014150:Antipsychotic Agents