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California verbal learning test-ii performance in schizophrenia as a function of ascertainment strategy: Comparing the first and second phases of the consortium on the genetics of schizophrenia (COGS)

  • Author(s): Stone, WS
  • Mesholam-Gately, RI
  • Braff, DL
  • Calkins, ME
  • Freedman, R
  • Green, MF
  • Greenwood, TA
  • Gur, RE
  • Gur, RC
  • Lazzeroni, LC
  • Light, GA
  • Nuechterlein, KH
  • Olincy, A
  • Radant, AD
  • Siever, LJ
  • Silverman, JM
  • Sprock, J
  • Sugar, CA
  • Swerdlow, NR
  • Tsuang, DW
  • Tsuang, MT
  • Turetsky, BI
  • Seidman, LJ
  • et al.
Abstract

© 2014. The first phase of the Consortium on the Genetics of Schizophrenia (COGS-1) showed performance deficits in learning and memory on the California Verbal Learning Test, Second Edition (CVLT-II) in individuals with schizophrenia (SZ), compared to healthy comparison subjects (HCS). A question is whether the COGS-1 study, which used a family study design (i.e. studying relatively intact families), yielded "milder" SZ phenotypes than those acquired subsequently in the COGS-2 case-control design that did not recruit unaffected family members. CVLT-II performance was compared for the COGS-1 and COGS-2 samples. Analyses focused on learning, recall and recognition variables, with age, gender and education as covariates. Analyses of COGS-2 data explored effects of additional covariates and moderating factors in CVLT-II performance. 324 SZ subjects and 510 HCS had complete CVLT-II and covariate data in COGS-1, while 1356 SZ and 1036 HCS had complete data in COGS-2. Except for recognition memory, analysis of covariance showed significantly worse performance in COGS-2 on all CVLT-II variables for SZ and HCS, and remained significant in the presence of the covariates. Performance in each of the 5 learning trials differed significantly. However, effect sizes comparing cases and controls were comparable across the two studies. COGS-2 analyses confirmed SZ performance deficits despite effects of multiple significant covariates and moderating factors. CVLT-II performance was worse in COGS-2 than in COGS-1 for both the SZ and the HCS in this large cohort, likely due to cohort effects. Demographically corrected data yield a consistent pattern of performance across the two studies in SZ.

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