Major depressive disorder is associated with broad impairments on neuropsychological measures of executive function: a meta-analysis and review

Abstract

Cognitive impairments are now widely acknowledged as an important aspect of major depressive disorder (MDD), and it has been proposed that executive function (EF) may be particularly impaired in patients with MDD. However, the existence and nature of EF impairments associated with depression remain strongly debated. Although many studies have found significant deficits associated with MDD on neuropsychological measures of EF, others have not, potentially due to low statistical power, task impurity, and diverse patient samples, and there have been no recent, comprehensive, meta-analyses investigating EF in patients with MDD. The current meta-analysis uses random-effects models to synthesize 113 previous research studies that compared participants with MDD to healthy control participants on at least one neuropsychological measure of EF. Results of the meta-analysis demonstrate that MDD is reliably associated with impaired performance on neuropsychological measures of EF, with effect sizes ranging from 0.32 to 0.97. Although patients with MDD also have slower processing speed, motor slowing alone cannot account for these results. In addition, some evidence suggests that deficits on neuropsychological measures of EF are greater in patients with more severe current depression symptoms, and those taking psychotropic medications, whereas evidence for effects of age was weaker. The results are consistent with the theory that MDD is associated with broad impairment in multiple aspects of EF. Implications for treatment of MDD and theories of EF are discussed. Future research is needed to establish the specificity and causal link between MDD and EF impairments.

Figure 1

Weighted mean effect sizes for all analyses. Error bars are 95% confidence intervals. Compared to healthy control participants, patients with MDD are significantly impaired on all tasks. EF composite measures are indicated with diamond symbols, and individual measures within each EF component by circle symbols in the same color. Pink circles indicate non-EF comparison measures. The solid vertical line indicates the psychomotor speed composite score effect size: measures for which the lower error b ar (95% confidence interval) does not pass the grey line have significantly larger effect sizes than the psychomotor speed effect size. Comp. = composite score; WCST = Wisconsin Card Sorting Test; TMT-B = Trail Making Test part B; TMT-A = Trail Making Test part A; ID/ED = Intradimensional/Extradimensional; WM = working memory; DMTS = delayed-match-to-sample; VF = verbal fluency.