Factor structure and heritability of endophenotypes in schizophrenia: Findings from the Consortium on the Genetics of (COGS-1)

© 2015 Elsevier B.V. Background: Although many endophenotypes for schizophrenia have been studied individually, few studies have examined the extent to which common neurocognitive and neurophysiological measures reflect shared versus unique endophenotypic factors. It may be possible to distill individual endophenotypes into composite measures that reflect dissociable, genetically informative elements. Methods: The first phase of the Consortium on the Genetics of Schizophrenia (COGS-1) is a multisite family study that collected neurocognitive and neurophysiological data between 2003 and 2008. For these analyses, participants included schizophrenia probands (n=. 83), their nonpsychotic siblings (n=. 151), and community comparison subjects (n=. 209) with complete data on a battery of 12 neurocognitive tests (assessing domains of working memory, declarative memory, vigilance, spatial ability, abstract reasoning, facial emotion processing, and motor speed) and 3 neurophysiological tasks reflecting inhibitory processing (P50 gating, prepulse inhibition and antisaccade tasks). Factor analyses were conducted on the measures for each subject group and across the entire sample. Heritability analyses of factors were performed using SOLAR. Results: Analyses yielded 5 distinct factors: 1) Episodic Memory, 2) Working Memory, 3) Perceptual Vigilance, 4) Visual Abstraction, and 5) Inhibitory Processing. Neurophysiological measures had low associations with these factors. The factor structure of endophenotypes was largely comparable across probands, siblings and controls. Significant heritability estimates for the factors ranged from 22% (Episodic Memory) to 39% (Visual Abstraction). Conclusions: Neurocognitive measures reflect a meaningful amount of shared variance whereas the neurophysiological measures reflect largely unique contributions as endophenotypes for schizophrenia. Composite endophenotype measures may inform our neurobiological and genetic understanding of schizophrenia. Background: Althoughmanyendophenotypesforschizophreniahavebeenstudiedindividually,fewstudieshave examined the extent to which common neurocognitive and neurophysiological measures re ﬂ ect shared versus uniqueendophenotypicfactors.Itmaybepossibletodistillindividualendophenotypesintocompositemeasures that re ﬂ ect dissociable, genetically informative elements. Methods: The ﬁ rstphaseoftheConsortiumontheGeneticsofSchizophrenia (COGS-1)isa multisitefamilystudy that collected neurocognitive and neurophysiological data between 2003 and 2008. For these analyses, participants included schizophrenia probands ( n = 83), their nonpsychotic siblings ( n = 151), and community com- parison subjects ( n = 209) with complete data on a battery of 12 neurocognitive tests (assessing domains of working memory, declarative memory, vigilance, spatial ability, abstract reasoning, facial emotion processing, andmotorspeed)and3neurophysiologicaltasksre ﬂ ectinginhibitoryprocessing(P50gating,prepulseinhibition and antisaccade tasks). Factor analyses were conducted on the measures for each subject group and across the entire sample. Heritability analyses of factors were performed using SOLAR. Results: sualAbstraction,and5)InhibitoryProcessing.Neurophysiologicalmeasureshadlowassociationswiththesefactors. The factor structure of endophenotypes was largely comparable across probands, siblings and controls. Signi ﬁ cant heritability estimates for the factors ranged from 22% (Episodic Memory) to 39% (Visual Abstraction). Conclusions: Neurocognitivemeasuresre ﬂ ectameaningfulamountofsharedvariancewhereastheneurophysiolog- icalmeasuresre ﬂ ectlargelyuniquecontributionsasendophenotypesforschizophrenia.Compositeendophenotype measures may inform our neurobiological and genetic understanding of schizophrenia. © 2015 Elsevier B.V. rights reserved.