Psychiatry Investig.  2021 Sep;18(9):850-863. 10.30773/pi.2021.0074.

Cortical Thickness and Surface Area Abnormalities in Bipolar I and II Disorders

• Woo Y
• Kang W
• Kang Y
• Kim A
• Han KM
• Tae WS
• Ham BJ

• KMID: 2520276
• DOI: http://doi.org/10.30773/pi.2021.0074

Abstract

Objective
Although bipolar II disorder (BD II) is not simply a mitigated form of bipolar I disorder (BD I), their neurobiological differences have not been elucidated. The present study aimed to explore cortical thickness (CT) and surface area (SA) in patients with BD I and BD II and healthy controls (HCs) to investigate the shared and unique neurobiological mechanisms of BD subtypes.
Methods
We enrolled 30 and 44 patients with BD I and BD II, respectively, and 100 HCs. We evaluated CT and SA using FreeSurfer and estimated differences in CT and SA among the three groups (BD I vs. BD II vs. HC). We adjusted for age, sex, educational level, and intracranial volume as confounding factors.
Results
We found widespread cortical thinning in the bilateral frontal, temporal, and occipital regions; cingulate gyrus; and insula in patients with BD. Alterations in SA, including increased SA of the pars triangularis and decreased SA of the insula, were noted in patients with BD. Overall, we found BD II patients demonstrated decreased SA in the right long insula compared to BD I patients.
Conclusion
Our results suggest that decreased SA in the right long insula is crucial for differentiating BD subtypes.

Keyword

Cortical thickness; Surface area; Bipolar disorder; Bipolar subtype; Long insula