title: Less unique variance than meets the eye: overlap among traditional neuropsychological dimensions in schizophrenia.
abstract: The magnitude of the overlap among dimensions of neuropsychological test performance in schizophrenia has been the subject of perennial controversy. This issue has taken on renewed importance with the recent focus on cognition as a treatment target in schizophrenia. A substantial body of factor analytic literature indicates that dimensions are separable in schizophrenia. However, this literature is generally uninformative as to whether the separable dimensions are independent, weakly correlated, or strongly correlated. Factor analyses have often used methods (ie, principal components analysis with orthogonal rotation) that preclude this determination, and correlations among factor-based domain composites and underlying measures have been reported infrequently in these studies. Current meta-analyses of reported "between-dimension" correlations for individual neuropsychological measures and for cognitive domain composite variables indicate that cognition variables in schizophrenia are correlated, on average, at a "medium" level of r = 0.37 for individual measures from different cognitive dimensions and r = 0.45 for domain composites. Because these are mean bivariate correlations, the multiple correlation of an individual measure with all the other measures in a cognitive battery is likely to be higher. Measure reliabilities of 0.80 or less also imply greater commonality among traditional neuropsychological measures. In short, there are underappreciated constraints on the amount of reliable cognitive performance variance in traditional neuropsychological test batteries that is free to vary independently. The ability of such batteries to reveal cognitive domain-specific treatment effects in schizophrenia may be much more limited than is generally assumed.
authors: VISN 5 Mental Illness Research, Education and Clinical Center, Baltimore, MD 21201, USA. Dwight.Dickinson@va.gov
authors: Dwight
authors: D
authors: Dickinson
authors: James M
authors: JM
authors: Gold
mesh_terms: D003072:Cognition Disorders / Q000175:diagnosis* / Q000453:epidemiology*; D015928:Cognitive Behavioral Therapy / Q000379:methods*; D006801:Humans; D009483:Neuropsychological Tests; D012559:Schizophrenia / Q000175:diagnosis / Q000453:epidemiology* / Q000628:therapy; D012720:Severity of Illness Index
references: Arch Gen Psychiatry. 2000 Mar;57(3):249-58
references: 10711911
references: Psychopharmacology (Berl). 2006 Aug;187(3):356-63
references: 16783539
references: J Nerv Ment Dis. 2000 Aug;188(8):518-24
references: 10972571
references: Arch Gen Psychiatry. 2001 Jan;58(1):24-32
references: 11146755
references: Biol Psychiatry. 2001 Jul 15;50(2):98-107
references: 11527000
references: Neuropsychopharmacology. 2001 Nov;25(5):777-88
references: 11682261
references: Am J Psychiatry. 2002 May;159(5):838-44
references: 11986139
references: Biol Psychiatry. 2002 Jun 15;51(12):972-8
references: 12062881
references: Assessment. 2002 Jun;9(2):171-80
references: 12066832
references: Br J Psychiatry Suppl. 2002 Sep;43:s85-90
references: 12271806
references: J Clin Exp Neuropsychol. 2002 Oct;24(7):873-82
references: 12647766
references: J Clin Psychiatry. 2003 May;64(5):524-31
references: 12755654
references: Schizophr Res. 2003 Jul 1;62(1-2):93-103
references: 12765749
references: Neuropsychopharmacology. 2003 Aug;28(8):1491-500
references: 12799617
references: Am J Psychiatry. 2003 Oct;160(10):1809-16
references: 14514495
references: Psychopharmacology (Berl). 2003 Sep;169(3-4):404-11
references: 12590356
references: Neuropsychology. 2003 Oct;17(4):539-47
references: 14599267
references: Schizophr Res. 2004 May 1;68(1):49-63
references: 15037339
references: Schizophr Res. 2004 May 1;68(1):95-102
references: 15037343
references: Biol Psychiatry. 2004 Apr 15;55(8):826-33
references: 15050864
references: Schizophr Res. 2004 Jun 1;68(2-3):283-97
references: 15099610
references: Am J Psychiatry. 2004 Jun;161(6):985-95
references: 15169686
references: Neuropsychopharmacology. 2004 Jul;29(7):1363-73
references: 15085092
references: Neuropsychopharmacology. 2004 Jul;29(7):1378-85
references: 15138435
references: Schizophr Res. 2004 Dec 1;71(2-3):273-83
references: 15474898
references: Am J Psychiatry. 1995 Jan;152(1):6-15
references: 7802121
references: Schizophr Res. 1996 May;20(1-2):29-32
references: 8794491
references: J Neuropsychiatry Clin Neurosci. 1996 Fall;8(4):423-8
references: 9116479
references: Arch Gen Psychiatry. 1997 Feb;54(2):159-65
references: 9040284
references: Schizophr Res. 1997 Apr 11;24(3):299-310
references: 9134590
references: Schizophr Res. 1997 Oct 17;27(1):11-9
references: 9373890
references: Eur Arch Psychiatry Clin Neurosci. 1998;248(2):70-7
references: 9684915
references: Psychiatry Res. 1998 Jun 15;79(2):139-49
references: 9705052
references: Schizophr Res. 1998 Nov 9;34(1-2):87-94
references: 9824880
references: Schizophr Bull. 1999;25(2):321-35
references: 10416734
references: Schizophr Res. 2004 Dec 15;72(1):11-9
references: 15531403
references: Neuropsychopharmacology. 2006 Sep;31(9):2033-46
references: 16641947
references: Schizophr Res. 2006 Oct;87(1-3):246-53
references: 16859898
references: Schizophr Res. 2007 Feb;90(1-3):316-24
references: 17141477
references: Neuropsychopharmacology. 2008 Feb;33(3):480-90
references: 17443126
references: Schizophr Res. 2004 Dec 15;72(1):29-39
references: 15531405
references: Am J Psychiatry. 2005 Jan;162(1):110-7
references: 15625208
references: Schizophr Bull. 2004;30(4):739-54
references: 15957196
references: Schizophr Res. 2005 Sep 1;77(1):43-58
references: 16005384
references: Schizophr Bull. 2005 Oct;31(4):810-5
references: 16107584
references: Biol Psychiatry. 2006 Jan 15;59(2):97-105
references: 16140282
references: J Psychiatr Res. 2006 Apr;40(3):200-6
references: 16039670
references: Neuropsychopharmacology. 2006 Mar;31(3):637-43
references: 16160711
references: Arch Gen Psychiatry. 2006 Jun;63(6):630-8
references: 16754836
references: Schizophr Res. 2006 Jul;85(1-3):20-9
references: 16616831
references: J Cogn Neurosci. 2000 Jan;12(1):223-32
references: 10769318