Are major depression and bipolar disorder neuropsychologically distinct? A meta-analysis of comparative studies.
Neuropsychological deficits are present in both major depression and bipolar disorder. So far, however, reports directly comparing these mood disorders with regard to cognitive outcomes have been scant and yielded inconsistent results. This work aims to combine the findings of comparative studies of cognition in major depression and bipolar disorder in order to explore whether these neuropsychiatric conditions present with distinct cognitive features.



The main online databases were extensively searched to retrieve reports assessing neurocognitive functioning in two groups of mood disorder patients, one with major depressive disorder and another with bipolar disorder, both in the same phase of illness. Between-group effect sizes for cognitive variables were obtained from selected studies and pooled by means of meta-analytic procedures.



During euthymia, a significant overall effect size (Hedges'g=0.64, P<0.001) favoring major depressive disorder was found for verbal memory as assessed with list learning tests, whereas no significant between-group differences were found for the remaining variables analyzed. During depressive episodes, similar cognitive outcomes were observed between groups.



At present, it is not possible to postulate specific neuropsychological profiles for major depression and bipolar disorder in light of available evidence. It remains to be ascertained whether the differences found for verbal memory constitute an expression of distinct underlying mechanisms or whether they are best explained by sample characteristics or differential exposure to variables with a negative impact on cognition.
Bipolar Disorder Program, Institute of Neurosciences, Favaloro University, Buenos Aires, Argentina; National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina; School of Psychology, University of Buenos Aires, Buenos Aires, Argentina.
C
C
Samamé
Bipolar Disorder Program, Institute of Neurosciences, Favaloro University, Buenos Aires, Argentina; Psychiatric Emergencies Hospital Torcuato de Alvear, Buenos Aires, Argentina.
A G
AG
Szmulewicz
National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina; Psychiatric Emergencies Hospital Torcuato de Alvear, Buenos Aires, Argentina.
M P
MP
Valerio
Bipolar Disorder Program, Institute of Neurosciences, Favaloro University, Buenos Aires, Argentina; National Scientific and Technical Research Council (CONICET), Buenos Aires, Argentina.
D J
DJ
Martino
Bipolar Disorder Program, Institute of Neurosciences, Favaloro University, Buenos Aires, Argentina; Institute of Cognitive Neurology (INECO), Buenos Aires, Argentina. Electronic address: sstreji@gmail.com.
S A
SA
Strejilevich
D000328:Adult; D001714:Bipolar Disorder / Q000453:epidemiology* / Q000523:psychology; D003071:Cognition; D003072:Cognition Disorders / Q000453:epidemiology* / Q000523:psychology; D003865:Major Depressive Disorder / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D008297:Male; D008568:Memory; D009483:Neuropsychological Tests; D011569:Psychiatric Status Rating Scales
Bipolar disorder; Cognitive functioning; Major depressive disorder; Meta-analysis