Severity of thought disorder predicts psychosis in persons at clinical high-risk

Schizophr Res. 2015 Dec;169(1-3):169-177. doi: 10.1016/j.schres.2015.09.008. Epub 2015 Oct 4.


Background: Improving predictive accuracy is of paramount importance for early detection and prevention of psychosis. We sought a symptom severity classifier that would improve psychosis risk prediction.

Methods: Subjects were from two cohorts of the North American Prodrome Longitudinal Study. All subjects met Criteria of Psychosis-Risk States. In Cohort-1 (n=296) we developed a classifier that included those items of the Scale of Psychosis-Risk Symptoms that best distinguished subjects who converted to psychosis from nonconverters, with performance initially validated by randomization tests in Cohort-1. Cohort-2 (n=592) served as an independent test set.

Results: We derived 2-Item and 4-Item subscales. Both included unusual thought content and suspiciousness; the latter added reduced ideational richness and difficulties with focus/concentration. The Concordance Index (C-Index), a measure of discrimination, was similar for each subscale across cohorts (4-Item subscale Cohort-2: 0.71, 95% CI=[0.64, 0.77], Cohort-1: 0.74, 95% CI=[0.69, 0.80]; 2-Item subscale Cohort-2: 0.68, 95% CI=[0.3, 0.76], Cohort-1: 0.72, 95% CI=[0.66-0.79]). The 4-Item performed better than the 2-Item subscale in 742/1000 random selections of 80% subsets of Cohort-2 subjects (p-value=1.3E-55). Subscale calibration between cohorts was proportional (higher scores/lower survival), but absolute conversion risk predicted from Cohort-1 was higher than that observed in Cohort-2, reflecting the cohorts' differences in 2-year conversion rates (Cohort-2: 0.16, 95% CI=[0.13, 0.19]; Cohort-1: 0.30, 95% CI=[0.24, 0.36]).

Conclusion: Severity of unusual thought content, suspiciousness, reduced ideational richness, and difficulty with focus/concentration informed psychosis risk prediction. Scales based on these symptoms may have utility in research and, assuming further validation, eventual clinical applications.

Keywords: High-risk; Psychosis; Risk prediction; Schizophrenia; Survival; Symptom severity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adolescent
  • Cognition Disorders / diagnosis
  • Cognition Disorders / etiology*
  • Cohort Studies
  • Female
  • Humans
  • Male
  • Neuropsychological Tests
  • Psychiatric Status Rating Scales
  • Psychotic Disorders / complications*
  • Psychotic Disorders / psychology
  • ROC Curve
  • Reproducibility of Results
  • Risk Factors
  • Survival Analysis
  • Thinking / physiology*
  • Young Adult