Neuropsychological testing of cognitive impairment in euthymic bipolar disorder: an individual patient data meta-analysis.

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.

Clinical and neurocognitive correlates of insight in patients with bipolar I disorder in remission.

OBJECTIVE: The relationship between insight and neurocognition in bipolar disorder has not been clearly established. METHOD: A neuropsychological battery assessing attention, mental control, perceptual-motor skills, executive functions, verbal fluency and abstraction, and visuo-spatial attention was administered to 50 bipolar remitted patients and 50 healthy controls. Insight was assessed with the Scale to Assess Unawareness of Mental Disorder. RESULTS: Patients presented significantly worse neurocognitive performance. Insight was impaired in 60% of patients, and age, educational level, manic symptoms, age of disease onset, number of admissions, and performance on several neurocognitive tests correlated significantly with insight. A regression model revealed that age and Trail Making Test part B (TMT-B) performance accounted for 32% of the variance in overall illness awareness, while performance on the TMT-B alone accounted for 28% of the variance. CONCLUSION: Impaired insight and neurocognitive dysfunction seem to be present in euthymic bipolar patients. Insight in bipolar disorder may be partially dependent on intact neurocognition.