Alterations of structural-functional coupling in bipolar disorder patients with suicidal ideation correlated with chronotype.

BACKGROUND

Bipolar disorder (BD) carries high suicidality risk. While suicidal ideation (SI) correlates with evening chronotype, their joint neuroimaging mechanisms remain unclear. Unimodal MRI lacks sensitivity to detect coupled structural-functional abnormalities. We hypothesized BD patients with SI (BD-SI) would exhibit altered structural connectivity-functional connectivity (SC-FC) coupling versus BD patients without SI (BD-nSI) and healthy controls (HC), potentially correlating with chronotype.

METHODS

We recruited 138 BD-SI, 46 BD-nSI, and 280 HC. Resting-state functional MRI (rs-fMRI) and diffusion tensor imaging (DTI) data were acquired, and chronotype was assessed by Morningness-Eveningness Questionnaire (MEQ). Structural/functional connectivity and SC-FC coupling were compared across groups. Associations between SI, chronotype, and altered SC-FC coupling were examined in BD-SI group.

RESULTS

We found an altered functional connectivity (FC) network between 3 groups, involving the caudate nucleus, putamen, supplementary motor area, postcentral gyrus, inferior temporal gyrus and fusiform gyrus as important nodes. BD-SI patients demonstrated the most pronounced evening chronotype shift in MEQ total scores. BD-SI patients showed reduced SC-FC coupling in the triangular part of right inferior frontal gyrus (IFGtriang.R) compared to BD-nSI and HC, while both BD subgroups exhibited decreased coupling in the right olfactory cortex (OLF.R) relative to HC. The right amygdala (AMYG.R) displayed increased coupling in BD-SI versus BD-nSI, however, its nominal association with evening chronotype in BD-SI patients did not survive multiple comparisons correction.

CONCLUSION

Our study reveals changes in SC-FC coupling and a significant eveningness chronotype in BD-SI patients. This conjunction of physiological and clinical features warrants further investigation into chronotherapeutic strategies.