Cortical thickness, volume and surface area in patients with bipolar disorder types I and II

Abstract

IntroductionBipolar disorder (BD) is a common chronic psychiatric disorder characterized by mood disturbances with recurrent episodes of mania, hypomania and depression interspersed by euthymic periods. The disorder is not only associated with premature death, significant disability and impaired psychosocial functioning, 1 but also with cognitive impairments. 2Summarizing previous imaging studies of patients with BD, recent meta-analyses and review articles have concluded that these patients demonstrate abnormalities primarily in frontal lobe regions, such as abnormally low volumes not only in the anterior cingulate cortex (ACC), medial and inferior frontal, orbitofrontal, ventral and dorsolateral prefrontal cortices, but also in the temporal and insular cortices. 3-9There are 2 established subtypes of BD: type I and type II. The subtype BDII is distinguished from BDI mainly by the absence of full-blown manic episodes. This and the generally observed lower functional impairment in patients with BDII compared with BDI 10 has led some to describe BDII as a milder form of BDI. But this conclusion is not necessarily accurate, as BDII is characterized by shorter euthymic intervals, more depressive episodes, longer time spent in a state of depression, more comorbidities and greater perceived suffering than BDI. 11,12 The fact that patients with BDI and BDII manifest different symptoms and severity suggests partly different neurobiological mechanisms and pathophysiology. Despite this, most previous studies have focused on patients with BDI or on patients with BDI and BDII combined indiscriminately. The few and small studies that have investigated patients with BDI, BDII and healthy controls suggest that the subtypes are characterized by common neurobiological alterations that are less pronounced in patients with BDII.13-15 One study reported fewer case-control differences in grey matter Background: Bipolar disorder (BD) is a common chronic psychiatric disorder mainly characterized by episodes of mania, hypomania and depression. The disorder is associated with cognitive impairments and structural brain abnormalities, such as lower cortical volumes in primarily frontal brain regions than healthy controls. Although bipolar disorder types I (BDI) and II (BDII) exhibit different symptoms and severity, previous studies have focused on BDI. Furthermore, the most frequently investigated measure in this population is cortical volume. The aim of our study was to investigate abnormalities in patients with BDI and BDII by simultaneously analyzing cortical volume, thickness and surface area, which yields more information about disease-and symptom-related neurobiology. Methods: We used MRI to measure cortical volume, thickness and area in patients with BDI and BDII as well as in healthy controls. The large study cohort enabled us to adjust for important confounding factors. Results: We included 81 patients with BDI, 59 with BDII and 85 controls in our analyses. Cortical volume, thickness and surface area abnormalities were present ...

Machine learning in major depression: From classification to treatment outcome prediction

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“…The need for higher statistical power and convergence of the findings has motivated the production of several large voxel-based meta-analyses [11][12][13][14] , as well as large single-centre studies 15 . These structural studies have found decreased brain volume in BD in a specific set of brain regions including medial PFC, anterior cingulate cortex and ventrolateral PFC as well as the insula.…”