Neurocognitive Functioning in Severe Depression

Research has suggested that major depressive disorder can negatively impact neurocognitive functioning. Depression has been implicated in affecting many cognitive domains, including executive function, attention, memory, and psychomotor and processing speed. However, there has been limited examination of the relationship between neurocognitive functioning and depressive characteristics such as depression severity, depressive subtypes, number of depressive episodes, and episode duration. The primary goal of this study was to explore the relationship between neurocognitive functioning and depressive characteristics in severe unipolar major depressive disorder. Baseline socio-demographic, clinical, and neuropsychological information was examined in 145 inpatients enrolled in a large electroconvulsive therapy study (the Consortium for Research in ECT). Results revealed that depression severity was unrelated to global cognitive functioning and executive functioning. However, performance on certain neurocognitive variables accounted for 25% of the variability in the magnitude of depression severity. Various clinical dimensions of depression, including depressive subtype, number of episodes, and episode duration did not show a systematic relationship to neurocognitive functioning. Patients with psychotic depression performed similarly to patients without psychosis, and the ability to predict the presence of psychosis by neuropsychological performance was low. Those with atypical depression performed similarly to patients with typical depression, although patients with atypical depression showed better performance on a measure of verbal memory. No significant differences were found between subjects with multiple versus single episodes of depression, and the number of depressive episodes was unrelated to neurocognitive performance. These data indicate that the depressive characteristics examined were not systematically related to neurocognitive functioning among severely depressed patients in this well characterized and carefully selected sample.