Cortical thickness and surface area as an endophenotype in bipolar disorder type I patients and their first-degree relatives.

Nefize Yalin,Emel Ada,Ceren Hidiroglu,Aysegul Ozerdem,Berrin Cavusoglu,Matthew J Kempton,Zeliha Tunca,Andre Zugman,Nese Direk,Gizem Isik,Ayşe Er,Deniz Ceylan,Aybala Saricicek

doi:10.1016/j.nicl.2019.101695

Abstract

ObjectivesSo far, few studies have investigated cortical thickness (CT) and surface area (SA) measures in bipolar disorder type I (BDI) in comparison to a high genetic risk group such as first-degree relatives (FR). This study aimed to examine CT and SA differences between BDI, FR and healthy controls (HC).Methods3D T1 magnetic resonance images were acquired from 27 euthymic BDI patients, 24 unaffected FR and 29 HC. CT and SA measures were obtained with FreeSurfer version 5.3.0. Generalized estimating equations were used to compare CT and SA between groups. Group comparisons were repeated with restricting the FR group to 17 siblings (FR-SB) only.Results\\Mean age in years was 36.3 ± 9.5 for BDI, 32.1 ± 10.9 for FR, 34.7 ± 9.8 for FR-SB and 33.1 ± 9.0 for HC group respectively. BDI patients revealed larger SA of left pars triangularis (LPT) compared to HC (p = .001). In addition, increased SA in superior temporal cortex (STC) in FR-SB group compared to HC was identified (p = .0001).ConclusionsOur result of increased SA in LPT of BDI could be a disease marker and increased SA in STC of FR-SB could be a marker related with resilience to illness.

Highlights

Bipolar disorder (BD) is characterized by episodes of mania, hypomania and depression and the wellbeing state between the episodes called euthymia (American Psychiatric Association, 2000)
The following participants were excluded: 11 BD type I (BDI) patients were not euthymic at the time of the assessment; 7 BDI patients, 7 first-degree relatives (FR) and 14 healthy controls (HC) decided to withdraw from the study before MRI scanning; and 3 BDI patients, 4 FR and 1 HC were excluded for movement artifacts after MRI scanning
Demographic characteristics of the groups and the clinical variables for the BDI group are shown in Table 1 and 2

Summary

Introduction

Bipolar disorder (BD) is characterized by episodes of mania, hypomania and depression and the wellbeing state between the episodes called euthymia (American Psychiatric Association, 2000). One way to investigate vulnerability factors for highly heritable diseases like BD is an endophenotype based approach (Hasler et al, 2006). An endophenotype is a biomarker, which is heritable, associated with illness, state-independent, co-segregates with illness in families and is found at a higher rate in non-effected family members compared to general population (Gottesman and Gould, 2003). A wide variety of endophenotypes have been proposed in the psychiatric literature and advanced tools of neuroimaging such as structural magnetic resonance imaging (sMRI) promise to expand these further (Gottesman and Gould, 2003)

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