Background: Previous studies have shown that major depressive disorder (MDD) is associated with a variety of cognitive deficits, which can persist even in remitted states. Nevertheless, the relationship between the cognitive and affective symptoms in depression remains obscure. The aim of the present study was to explore the clinical characteristics and correlates of the cognitive deficits in patients with MDD. Methods: Clinical and neuropsychological assessments were conducted at baseline and 6-month follow-ups. The severity of the disease and the effect of treatment were assessed with the Hamilton Depression Scale-17. Neuropsychological tests, including the digital symbol substitution test and digit span test, were administered to 67 depressed patients and 56 healthy participants. Results: MDD patients showed impairments in memory, attention, and executive function at baseline. After the 6-month treatment phase, patients in remission showed significant alleviation of these cognitive deficits, although impairments in attention and executive function were still present when compared to controls. Discussion: Significant cognitive deficits are present in MDD. The speed of remission of cognitive functions seems to be slower than and inconsistent with emotional symptoms, which provides new support for the argument that cognitive deficits are independent factors from the emotional symptoms in MDD.

Objective The aim of the study was to explore the tendency of modified electroconvulsive therapy (MECT)-related working memory and subjective memory deficits in depressed patients. Methods Sixty patients with unipolar/bipolar depression were prepared and enrolled for MECT and 56 subjects were enrolled as healthy controls (HCs). Their demographics (sex, age, body mass index, years of schooling, etc) and clinical characteristics (dosage and number of MECT, etc) were compared. Depression severity, working memory, and subjective memory were measured using the Hamilton Depression Rating Scale 17 (HAMD17), a Digit Span Backwards (DSB), and self-reported assessments, respectively. Measurements were taken at baseline, within 24 hours after each MECT session, and in every month for a 6-month follow-up period. Results (a) The patients had poorer performance than the HCs on DSB and HAMD17 at baseline, and the DSB score and HAMD17 total scores were negatively correlated. However, after the second MECT session, the patients' HAMD17 score was significantly improved compared with that at the baseline (P < 0.05), whereas the DSB score showed no significant difference compared with the HCs (P > 0.05). (b) After the first MECT session, 62% of the patients reported subjective memory deficits, which were exacerbated over the subsequent sessions and relieved with antidepressant treatment during the follow-up period. (c) The risk factors for prolonged subjective memory deficits were overweight and the maximum MECT dosage/age (dosage/age = the percentage of output part of total dosage × 100/age, unit: 1/year) ≥ 1.5/year (odds ratio [OR] = 15.36 and 7.98). Conclusions Depressed patients showed poorer working memory than the HCs. Such memory deficit may be aggravated by MECT, although it may improve with the relief of depression. Although subjective memory deficits can occur after the first MECT session and gradually recover after the treatment, they may last for 6 months or longer. Persistent deficits may be related to being overweight and having a high MECT dosage.