Neurocognitive function of patients with melancholic and non-melancholic major depressive episodes: An exploratory study

Objective: The aim of this exploratory study was to compare the neurocognitive performance of patients undergoing melancholic and non-melancholic major depressive episodes. Considering potential limitations of the Diagnostic and Statistical Manual of Mental Disorders (5th ed.) specifier, we employed an additional tool that has proven useful in identifying melancholia (the Sydney Melancholia Prototype Index). Methods: One hundred forty-one depressed inpatients were classified as melancholic or non-melancholic according to the Sydney Melancholia Prototype Index and the Diagnostic and Statistical Manual of Mental Disorders (5th ed.) criteria and compared on a neurocognitive battery selected to assess attention and processing speed, verbal memory, working memory and executive functions. Results were controlled for several potential confounders. Results: Patients diagnosed as melancholic by the two diagnostic systems displayed lower scores in executive measures, semantic verbal fluency and phonological verbal fluency. On attention and processing speed, patients with melancholia underperformed those with non-melancholic depression only when diagnosed by the Sydney Melancholia Prototype Index. After controlling for confounders, associations between melancholic status and executive dysfunction remained significant for the Sydney Melancholia Prototype Index but not for the Diagnostic and Statistical Manual of Mental Disorders (5th ed.) diagnosis. Conclusion: In this study, melancholia diagnosed by the Sydney Melancholia Prototype Index (but not by the Diagnostic and Statistical Manual of Mental Disorders [5th ed.] criteria) was characterized by a greater compromise of tests assessing executive functions than non-melancholic depressions, even after controlling for depressive severity. These preliminary results might contribute to generating hypotheses about differences in the cognitive profile and pathophysiological substrate between melancholic and non-melancholic depressions. Likewise, the pattern of findings supports the hypothesis that the Diagnostic and Statistical Manual of Mental Disorders (5th ed.) melancholia specifier might identify more severe forms of depressive episodes rather than a qualitatively different subtype.