Sex differences in cognitive function of first-diagnosed and drug-naïve patients with bipolar disorder

Background: Bipolar disorder (BD) is a severe mental illness that affects more than 1% the world's population with high recurrence rates and a series of comorbidities. Cognitive dysfunction is an endophenotype of BD, but sex influences in cognitive impairment remains unclear.

Method: We evaluated the performance of 139 patients with first-diagnosed, drug-naïve BD (44 males and 95 females) and 92 healthy controls (24 males and 68 females) using the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) scale and the Stroop color-word test.

Result: Immediate memory, visuospatial/constructional ability, language, attention, delayed memory, total RBANS score, and Stroop color-word scores were significantly lower in patients with first-diagnosed, drug-naïve BD than healthy participants. Thus, male patients had worse attention and delayed memory scores compared with female patients with BD. Importantly, a worse performance in visuospatial/constructional ability was negatively associated with the Young Mania Rating Scale score in male patients only.

Conclusion: Male patients with first-diagnosed, drug-naïve bipolar disorder had worse cognitive dysfunction than female patients in attention and delayed memory. Cognitive deficits were correlated with mania severity only in male patients. These findings reveal the sexual dimorphism in the cognitive deficits of early BD patients with mild and moderated symptoms for further pathophysiological exploration.