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. 2018 Jun 6;44(4):908-921.
doi: 10.1093/schbul/sbx141.

Assessment of Cognition and Personality as Potential Endophenotypes in the Western Australian Family Study of Schizophrenia

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Assessment of Cognition and Personality as Potential Endophenotypes in the Western Australian Family Study of Schizophrenia

Nina S McCarthy et al. Schizophr Bull. .
Free PMC article

Abstract

Phenotypic heterogeneity is a major barrier to understanding the genetic architecture underlying schizophrenia. Incorporating endophenotypes is one way to reduce heterogeneity and facilitate more powerful genetic analysis. Candidate endophenotypes require systematic assessment against endophenotype criteria, and a ranking of their potential utility for genetic analysis. In this study we assess 20 cognitive and personality measures in a sample of 127 families with at least 2 cases of schizophrenia per family (n = 535) plus a set of 30 control families (n = 121) against 4 endophenotype criteria: (a) be associated with the illness but not be a part of its diagnosis, (b) be heritable, (c) co-segregate with the illness in families, and (d) be found in unaffected relatives at a higher rate than in the general population. The endophenotype ranking score (endophenotype ranking variable [ERV]) was used to rank candidate endophenotypes based on their heritability and genetic correlation with schizophrenia. Finally, we used factor analysis to explore latent factors underlying the cognitive and personality measures. Evidence for personality measures as endophenotypes was at least equivalent to that of the cognitive measures. Factor analysis indicated that personality and cognitive traits contribute to independent latent dimensions. The results suggest for this first time that a number of cognitive and personality measures are independent and informative endophenotypes. Use of these endophenotypes in genetic studies will likely improve power and facilitate novel aetiological insights.

Figures

Fig. 1.
Fig. 1.
Genetic correlation (ρg) between candidate endophenotypes and schizophrenia. Only significantly heritable traits were assessed for genetic correlation. The genetic correlation (dark grey) as a proportion of the phenotypic correlation (Pearson’s r) with schizophrenia (light grey) is shown. *q < .05, **q < .01. Other abbreviations as shown in Table 1.
Fig. 2.
Fig. 2.
Traits with significant heritability and genetic correlation with schizophrenia with their endophenotype ranking variable (ERV). Personality traits are shown as triangles, cognitive traits as circles. TCI, Temperament and Character Inventory; SPQ, Schizotypal Personality Questionnaire; CPT-IP, Continuous Performance Task identical pairs; IT, inspection time; RAVLT-DW, Rey Auditory Verbal Learning Test delayed word recall; RAVLT-IW, Rey Auditory Verbal Learning Test immediate word recall; NART, National Adult Reading Test IQ.

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