OBJECTIVE: An association between bipolar disorder and cognitive impairment has repeatedly been described, even for euthymic patients. Findings are inconsistent both across primary studies and previous meta-analyses. This study reanalysed 31 primary data sets as a single large sample (N = 2876) to provide a more definitive view. METHOD: Individual patient and control data were obtained from original authors for 11 measures from four common neuropsychological tests: California or Rey Verbal Learning Task (VLT), Trail Making Test (TMT), Digit Span and/or Wisconsin Card Sorting Task. RESULTS: Impairments were found for all 11 test-measures in the bipolar group after controlling for age, IQ and gender (Ps ≤ 0.001, E.S. = 0.26-0.63). Residual mood symptoms confound this result but cannot account for the effect sizes found. Impairments also seem unrelated to drug treatment. Some test-measures were weakly correlated with illness severity measures suggesting that some impairments may track illness progression. CONCLUSION: This reanalysis supports VLT, Digit Span and TMT as robust measures of cognitive impairments in bipolar disorder patients. The heterogeneity of some test results explains previous differences in meta-analyses. Better controlling for confounds suggests deficits may be smaller than previously reported but should be tracked longitudinally across illness progression and treatment.
OBJECTIVE: An association between bipolar disorder and cognitive impairment has repeatedly been described, even for euthymic patients. Findings are inconsistent both across primary studies and previous meta-analyses. This study reanalysed 31 primary data sets as a single large sample (N = 2876) to provide a more definitive view. METHOD: Individual patient and control data were obtained from original authors for 11 measures from four common neuropsychological tests: California or Rey Verbal Learning Task (VLT), Trail Making Test (TMT), Digit Span and/or Wisconsin Card Sorting Task. RESULTS: Impairments were found for all 11 test-measures in the bipolar group after controlling for age, IQ and gender (Ps ≤ 0.001, E.S. = 0.26-0.63). Residual mood symptoms confound this result but cannot account for the effect sizes found. Impairments also seem unrelated to drug treatment. Some test-measures were weakly correlated with illness severity measures suggesting that some impairments may track illness progression. CONCLUSION: This reanalysis supports VLT, Digit Span and TMT as robust measures of cognitive impairments in bipolar disorder patients. The heterogeneity of some test results explains previous differences in meta-analyses. Better controlling for confounds suggests deficits may be smaller than previously reported but should be tracked longitudinally across illness progression and treatment.
Authors: Alysa E Doyle; Pieter J Vuijk; Nathan D Doty; Lauren M McGrath; Brian L Willoughby; Ellen H O'Donnell; H Kent Wilson; Mary K Colvin; Deanna C Toner; Kelsey E Hudson; Jessica E Blais; Hillary L Ditmars; Stephen V Faraone; Larry J Seidman; Ellen B Braaten Journal: J Int Neuropsychol Soc Date: 2017-08-04 Impact factor: 2.892
Authors: Ariel G Gildengers; Meryl A Butters; Howard J Aizenstein; Megan M Marron; James Emanuel; Stewart J Anderson; Lisa A Weissfeld; James T Becker; Oscar L Lopez; Benoit H Mulsant; Charles F Reynolds Journal: Bipolar Disord Date: 2014-09-25 Impact factor: 6.744
Authors: Alison K Merikangas; Lihong Cui; Monica E Calkins; Tyler M Moore; Ruben C Gur; Raquel E Gur; Kathleen R Merikangas Journal: J Affect Disord Date: 2017-03-10 Impact factor: 4.839
Authors: J Volkert; M A Schiele; Julia Kazmaier; Friederike Glaser; K C Zierhut; J Kopf; S Kittel-Schneider; A Reif Journal: Eur Arch Psychiatry Clin Neurosci Date: 2015-11-26 Impact factor: 5.270