Biochemical metabolism in the anterior cingulate cortex and cognitive function in major depressive disorder with or without insomnia syndrome

Background: Major depressive disorder (MDD) and insomnia have been linked to deficiencies in cognitive per-formance. However, the underlying mechanism of cognitive impairment in MDD patients with insomnia symptoms (IS) remains unclear. This study aimed to explore the effects of IS in patients with MDD by comparing cognitive function indices among those with IS, those without insomnia symptoms (NIS), and healthy controls (HCs). In addition, we assessed whether the dysfunction of central nervous system (CNS) is one of the important pathophysiologic mechanisms of IS in patients with MDD by comparing the biochemical metabolism ratios in the anterior cingulate cortex (ACC). Method: Fifty-five MDD with IS, 39 MDD without IS, and 47 demographically matched HCs underwent the MATRICS Consensus Cognitive Battery (MCCB) assessment and proton magnetic resonance spectroscopy (1H -MRS). MCCB cognitive scores and biochemical metabolism in ACC were assessed and compared between groups. Results: Compared to the HCs group, IS and NIS groups scored significantly lower in seven MCCB cognitive domains (speed of processing, attention/vigilance, working memory, verbal learning, visual learning, reasoning problem solving and social cognition). IS group showed a lower speed of processing and lower Cho/Cr ratio in the left ACC vs. NIS group and HCs. Also, in IS group, the Cho/Cr ratio in the left ACC was positively correlated with the composite T-score. Conclusion: Patients with comorbidity of MDD with IS may exhibit more common MCCB cognitive impairments than those without IS, particularly speed of processing. Also, dysfunction of ACC may underlie the neural sub-strate of cognitive impairment in MDD with IS.

Automated summary

This study aimed to compare cognitive function indices among patients with major depressive disorder (MDD) and insomnia symptoms (IS), MDD without IS, and healthy controls (HCs) to examine the effects of IS in MDD patients. Results showed that IS and NIS groups scored significantly lower in seven cognitive domains compared to HCs. The IS group also exhibited lower speed of processing and lower Cho/Cr ratio in the left anterior cingulate cortex (ACC), and the Cho/Cr ratio in the left ACC was positively correlated with the composite T-score in the IS group. Therefore, MDD patients with comorbid IS may experience more common cognitive impairments, particularly in speed of processing, and dysfunction of the ACC may contribute to cognitive impairment in MDD with IS.