Cognitive markers of psychotic unipolar depression: a meta-analytic study

The goal of the current meta-analysis was to review and examine in detail the features of cognitive performance in psychotic (MDDP) versus non-psychotic (MDD) major depressive disorder.

An electronic literature search was performed to find studies comparing cognitive performance in MDDP versus MDD. A meta-analysis of broad cognitive domains (processing speed, reasoning/problem solving, verbal learning, visual learning, attention/working memory) and individual cognitive tasks was conducted on all included studies (n=12). Demographic and clinical features were investigated via meta-regression analysis as moderators of cognitive performance.

No difference in socio-demographic and clinical variables was detected between groups. In general, a poorer cognitive performance was detected in MDDP versus MDD subjects (ES=0.38), with a greater effect size in drug-free patients (ES=0.69). MDDP patients were more impaired in verbal learning (ES=0.67), visual learning (ES=0.62) and processing speed (ES=0.71) tasks. A significantly poorer performance was also detected in MDDP patients for individual tasks as Trail Making Test A, WAIS-R digit span backward and WAIS-R digit symbol. Age resulted to have a negative effect on tasks involved in working memory performance.

In line with previous meta-analyses, our findings seem to support an association between psychosis and cognitive deficits in the context of affective disorders. Psychosis during the course of MDD is associated with poorer cognitive performance in some specific cognitive domains, such as visual and verbal learning and executive functions.