Gray matter volumes in symptomatic and asymptomatic offspring of parents diagnosed with bipolar disorder

Abstract

Children of parents diagnosed with bipolar disorder (BD), termed high-risk offspring (HRO), are at greater risk of developing psychiatric disorders compared to healthy children of healthy parents (HCO). Gray matter volume (GMV) abnormalities have been observed in HRO, however, these reports are inconsistent. We posit that this variability may be attributed to differences in methodology among offspring studies; in particular, the presence of psychiatric symptoms in HRO. Here, we directly compared GMVs between symptomatic and asymptomatic HRO, and HCO. High-resolution T1-weighted MR images were collected from 31 HRO (18 symptomatic and 13 asymptomatic) and 20 age- and sex-matched HCO. HRO had at least one parent diagnosed with BD. Symptomatic HRO were defined as having a psychiatric diagnosis other than BD, while asymptomatic HRO were required to be free of any psychiatric diagnosis. Scans were processed using voxel-based morphometry methods and between group analyses were performed in SPM. Compared to HCO, the HRO group showed decreased GMV in the right inferior orbitofrontal, right middle frontal, and bilateral superior and middle temporal regions. Both symptomatic and asymptomatic HRO groups showed decreased GMV in these regions separately when compared to HCO. When comparing symptomatic and asymptomatic HRO, GMVs were comparable in all regions except the lateral occipital cortex. Our study compared symptomatic and asymptomatic HRO directly. In doing so, we provided further support for the presence of discrete GMV deficits in HRO, and confirmed that these deficits are present irrespective of the presence of symptoms in HRO.

Keywords: Bipolar disorder; Bipolar offspring; Gray matter volumes; High-risk offspring; MRI; Voxel-based morphometry.