title: Neurocognitive performance in family-based and case-control studies of schizophrenia.
abstract: BACKGROUND
  Neurocognitive deficits in schizophrenia (SZ) are established and the Consortium on the Genetics of Schizophrenia (COGS) investigated such measures as endophenotypes in family-based (COGS-1) and case-control (COGS-2) studies. By requiring family participation, family-based sampling may result in samples that vary demographically and perform better on neurocognitive measures.
  
  
  METHODS
  The Penn computerized neurocognitive battery (CNB) evaluates accuracy and speed of performance for several domains and was administered across sites in COGS-1 and COGS-2. Most tests were included in both studies. COGS-1 included 328 patients with SZ and 497 healthy comparison subjects (HCS) and COGS-2 included 1195 patients and 1009 HCS.
  
  
  RESULTS
  Demographically, COGS-1 participants were younger, more educated, with more educated parents and higher estimated IQ compared to COGS-2 participants. After controlling for demographics, the two samples produced very similar performance profiles compared to their respective controls. As expected, performance was better and with smaller effect sizes compared to controls in COGS-1 relative to COGS-2. Better performance was most pronounced for spatial processing while emotion identification had large effect sizes for both accuracy and speed in both samples. Performance was positively correlated with functioning and negatively with negative and positive symptoms in both samples, but correlations were attenuated in COGS-2, especially with positive symptoms.
  
  
  CONCLUSIONS
  Patients ascertained through family-based design have more favorable demographics and better performance on some neurocognitive domains. Thus, studies that use case-control ascertainment may tap into populations with more severe forms of illness that are exposed to less favorable factors compared to those ascertained with family-based designs.
authors.forename: Ruben C
authors.initials: RC
authors.lastname: Gur
authors.forename: David L
authors.initials: DL
authors.lastname: Braff
authors.forename: Monica E
authors.initials: ME
authors.lastname: Calkins
authors.forename: Dorcas J
authors.initials: DJ
authors.lastname: Dobie
authors.forename: Robert
authors.initials: R
authors.lastname: Freedman
authors.forename: Michael F
authors.initials: MF
authors.lastname: Green
authors.forename: Tiffany A
authors.initials: TA
authors.lastname: Greenwood
authors.forename: Laura C
authors.initials: LC
authors.lastname: Lazzeroni
authors.forename: Gregory A
authors.initials: GA
authors.lastname: Light
authors.forename: Keith H
authors.initials: KH
authors.lastname: Nuechterlein
authors.forename: Ann
authors.initials: A
authors.lastname: Olincy
authors.forename: Allen D
authors.initials: AD
authors.lastname: Radant
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Seidman
authors.forename: Larry J
authors.initials: LJ
authors.lastname: Siever
authors.forename: Jeremy M
authors.initials: JM
authors.lastname: Silverman
authors.forename: Joyce
authors.initials: J
authors.lastname: Sprock
authors.forename: William S
authors.initials: WS
authors.lastname: Stone
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Sugar
authors.forename: Neal R
authors.initials: NR
authors.lastname: Swerdlow
authors.forename: Debby W
authors.initials: DW
authors.lastname: Tsuang
authors.forename: Ming T
authors.initials: MT
authors.lastname: Tsuang
authors.forename: Bruce I
authors.initials: BI
authors.lastname: Turetsky
authors.forename: Raquel E
authors.initials: RE
authors.lastname: Gur
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D003201:Computers; D058068:Endophenotypes; D015340:Epidemiologic Research Design; D005190:Family; D020022:Genetic Predisposition to Disease; D006801:Humans; D008875:Middle Aged; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000453:epidemiology* / Q000235:genetics; D012565:Schizophrenic Psychology; D055815:Young Adult