Melancholic versus non-melancholic depression: differences on cognitive function. A longitudinal study protocol

BACKGROUND: Cognitive dysfunction is common among depressed patients. However, the pattern and magnitude of impairment during episodes of major depressive disorder (MDD) through to clinical remission remains unclear. Heterogeneity of depressive patients and the lack of longitudinal studies may account for contradictory results in previous research. METHODS/DESIGN: This longitudinal study will analyze cognitive differences between CORE-defined melancholic depressed patients (n = 60) and non-melancholic depressed patients (n = 60). A comprehensive clinical and cognitive assessment will be performed at admission and after 6 months. Cognitive dysfunction in both groups will be longitudinally compared, and the persistence of cognitive impairment after clinical remission will be determined. DISCUSSION: The study of neuropsychological dysfunction and the cognitive changes through the different phases of depression arise a wide variety of difficulties. Several confounding variables must be controlled to determine if the presence of depression could be considered the only factor accounting for group differences.