Sex differences in the cognitive function of first-diagnosed, drug-naïve depressed patients: An observational case-control study.

Background: Major depressive disorder (MDD) is a severe mental illness with high prevalence and recurrence rates. Cognitive impairments are found in most depressed patients, but systematic assessment of sex differences in cognitive deficits remains to be investigated.

Methods: A total of 69 first-diagnosed, drug-naïve depressed outpatients (males/females = 28/41; average age: 27.51±8.82 years) and 57 healthy controls (HCs) (males/females = 26/31; average age: 29.05±8.69 years) were recruited. Cognitive function, measured by repeatable battery for the assessment of neuropsychological status [RBANS] scores, was compared between depressed patients and healthy controls in males and females.

Results: Immediate memory, delayed memory and RBANS total score were significantly decreased in depressed patients compared with healthy controls. Moreover, among patients with first-diagnosed, drug-naïve depression, females had lower visuospatial and constructional scores than males, whereas among controls, females had higher language scores than males. Interestingly, impaired attention was negatively associated with the Beck Depression Inventory-II (BDI-II) score in female patients, but not in male patients.

Conclusion: Female patients with first-diagnosed, drug-naïve depression had more serious cognitive impairment than male patients in the visuospatial and constructional categories. Cognitive impairment was associated with depression severity only in female patients. These observations build the basis for future investigation of sex differences in cognitive impairment of depressed patients.