A meta-analysis of cognitive performance in melancholic versus non-melancholic unipolar depression

- Overall, MEL show a poorer cognitive performance than NMEL.
- Working memory, visual learning and problem solving are more impaired in MEL.
- The difference is independent of age, treatments and severity of depression.

BackgroundRecently there is increasing recognition of cognitive dysfunction as a core feature of Major Depressive Disorder (MDD). The goal of the current meta-analysis was to review and examine in detail the specific features of cognitive dysfunction in Melancholic (MEL) versus Non-Melancholic (NMEL) MDD.MethodsAn electronic literature search was performed to find studies comparing cognitive performance in MEL versus NMEL. A meta-analysis of broad cognitive domains (processing speed, reasoning/problem solving, verbal learning, visual learning, attention/working memory) was conducted on all included studies (n=9). Sensitivity and meta-regression analyses were also conducted to detect possible effects of moderator variables (age, gender, education, symptom severity and presence of treatments).ResultsMEL patients were older and more severly depressed than NMEL subjects. The MEL group was characterized by a worse cognitive performance in attention/working memory (ES=−0.31), visual learning (ES=−0.35) and reasoning/problem solving (ES=−0.46). No difference was detected in drug-free patients by sensitivity analyses. No effect was found for any of our moderators on the cognitive performance in MEL vs NMEL.ConclusionOur findings seem to support a moderate but specific effect of melancholic features in affecting the cognitive performance of MDD, in particular as regards visual learning and executive functions.