Neurocognitive Characteristics of Major Depressive Disorder Measured by Degraded Continuous Performance Test

Abstract

Background: Depression is a prevalent mental health problem, representing the third major cause of disability worldwide. Besides mood symptoms, depression is characterized by cognitive impairment, which is believed to be one variable that reduces recovery, influences recurrence rates, and increases the risk of chronicity. However, the characteristics of cognitive impairment among depressive patients have not been sufficiently investigated so far, and clinical practice lacks objective tools to detect and measure it. Objectives: The study aims to investigate the neurocognitive patterns of major depressive disorder (MDD) and the association of those patterns with clinical symptoms, particularly with levels of daily functioning. Methods: To objectively measure neurocognitive impairment and the nature of cognitive functioning, a 12-min duration computerized degraded continuous performance test (CPT-DS) with three blocks (720 digits, 10% targets, degradation 40%) was administered to two groups: a study group consisting of patients with recurrent moderate MDD episodes with similar motor retardation, and a control group of healthy participants. Nonparametric correlational techniques (Spearman), Student's t-tests, or nonparametric Mann-Whitney (M-W) U-tests were applied for statistical analysis. Results: The following variables were analyzed: d' value (average reaction time and coefficient of variance for both correct reactions and commission errors), omission and commission errors, and the clinical parameter "Work and Activities" (item seven on HDRS). Depressed patients showed a significantly lower d' value and more omission errors than healthy controls. The number of omission errors was significantly positively correlated with the score on HDRS item seven. The d' value was negatively correlated with the identical item scores. Conclusions: In conclusion, our study showed that the CPT, which runs longer and requires more effort to complete the task (degraded version), is relatively sensitive in detecting the specific characteristics of cognitive impairment in depression. Some specific symptoms of depression, indicating the daily functioning of patients, are linked to decreased sustainability of attention and vigilance. This demonstrates that cognitive impairment is a different essential factor of depression, affecting the functioning of patients and emphasizing the need to introduce novel treatment strategies specifically targeting cognitive impairment in patients with MDD.