Do premorbid and post-onset cognitive functioning differ between schizophrenia and bipolar disorder? A systematic review and meta-analysis

TY - JOUR

T1 - Do premorbid and post-onset cognitive functioning differ between schizophrenia and bipolar disorder? A systematic review and meta-analysis

AU - Trotta, A.

AU - Murray, R. M.

AU - Maccabe, J. H.

PY - 2015/1/12

Y1 - 2015/1/12

N2 - Background Schizophrenia (SZ) is characterized by a broad global cognitive impairment that precedes the onset of the disease. By contrast, some studies suggest that premorbid deficits are absent, or even reversed, in bipolar disorder (BD). However, studies have shown impairments in cognitive functioning after the illness onset in both disorders. The aim of this study was to systematically review and meta-Analyze those studies that compared premorbid and/or post-onset global cognitive function between SZ and BD. Method We searched Medline (PubMed), EMBASE and PsycINFO for studies where information on cognitive functioning was collected in both SZ and BD within the same study or using the same methods. Results Compared to healthy comparison groups, SZ patients showed a significant premorbid cognitive impairment [standardized mean difference (SMD) -0.597, 95% confidence interval (CI) -0.707 to -0.487, p < 0.0001] and a large post-onset impairment (SMD -1.369, 95% CI -1.578 to -1.160, p < 0.0001). We found small significant deficits in premorbid intellectual function in the BD group when this was assessed retrospectively (-0.147, 95% CI -0.238 to -0.056, p = 0.001) but not prospectively (-0.029, 95% CI -0.199 to + 0.142, p = 0.744), and moderate cognitive impairment after onset (SMD -0.623, 95% CI -0.717 to -0.529, p < 0.0001). Conclusions SZ is characterized by significant deficits in premorbid intellectual function but the evidence regarding premorbid function in BD is equivocal. After illness onset, patients with both disorders seem to suffer a further decline in cognitive function but the magnitude of the impairment remains greater in SZ than in BD.

AB - Background Schizophrenia (SZ) is characterized by a broad global cognitive impairment that precedes the onset of the disease. By contrast, some studies suggest that premorbid deficits are absent, or even reversed, in bipolar disorder (BD). However, studies have shown impairments in cognitive functioning after the illness onset in both disorders. The aim of this study was to systematically review and meta-Analyze those studies that compared premorbid and/or post-onset global cognitive function between SZ and BD. Method We searched Medline (PubMed), EMBASE and PsycINFO for studies where information on cognitive functioning was collected in both SZ and BD within the same study or using the same methods. Results Compared to healthy comparison groups, SZ patients showed a significant premorbid cognitive impairment [standardized mean difference (SMD) -0.597, 95% confidence interval (CI) -0.707 to -0.487, p < 0.0001] and a large post-onset impairment (SMD -1.369, 95% CI -1.578 to -1.160, p < 0.0001). We found small significant deficits in premorbid intellectual function in the BD group when this was assessed retrospectively (-0.147, 95% CI -0.238 to -0.056, p = 0.001) but not prospectively (-0.029, 95% CI -0.199 to + 0.142, p = 0.744), and moderate cognitive impairment after onset (SMD -0.623, 95% CI -0.717 to -0.529, p < 0.0001). Conclusions SZ is characterized by significant deficits in premorbid intellectual function but the evidence regarding premorbid function in BD is equivocal. After illness onset, patients with both disorders seem to suffer a further decline in cognitive function but the magnitude of the impairment remains greater in SZ than in BD.

KW - Bipolar disorder

KW - cognitive function

KW - first episode

KW - intelligence

KW - meta-Analysis

KW - pre- and post-onset

KW - schizophrenia

KW - systematic review

UR - http://www.scopus.com/inward/record.url?scp=84927694738&partnerID=8YFLogxK

U2 - 10.1017/S0033291714001512

DO - 10.1017/S0033291714001512

M3 - Review article

AN - SCOPUS:84927694738

SN - 0033-2917

VL - 45

SP - 381

EP - 394

JO - Psychological Medicine

JF - Psychological Medicine

IS - 2

ER -