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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, William S
  • Mesholam-Gately, Raquelle I
  • Braff, David L
  • Calkins, Monica E
  • Freedman, Robert
  • Green, Michael F
  • Greenwood, Tiffany A
  • Gur, Raquel E
  • Gur, Ruben C
  • Lazzeroni, Laura C
  • Light, Gregory A
  • Nuechterlein, Keith H
  • Olincy, Ann
  • Radant, Allen D
  • Siever, Larry J
  • Silverman, Jeremy M
  • Sprock, Joyce
  • Sugar, Catherine A
  • Swerdlow, Neal R
  • Tsuang, Debby W
  • Tsuang, Ming T
  • Turetsky, Bruce I
  • Seidman, Larry J
  • et al.
Abstract

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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