Amygdala enlargement in unaffected offspring of bipolar parents

Abstract

Background: Bipolar disorder (BD) is a devastating disorder with a strong genetic component. While the frontolimbic profile of individuals suffering from BD is relatively well-established, there is still disagreement over the neuroanatomical features of unaffected BD offspring.

Material and methods: Brain volumetric measures were obtained for 82 children and adolescents including 18 unaffected BD offspring (10.50 ± 3.37 years), 19 BD offspring suffering from psychiatric disorders (12.87 ± 3.28 years) and 45 healthy controls (HC-10.50 ± 3.37 years). Clinical diagnoses were established according to the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria. Cortical reconstruction and volumetric segmentation were performed with the Freesurfer image analysis suite. Profile analyses compared frontolimbic volumes across groups. Age, gender, testing site, ethnicity and intracranial volume were entered as covariates.

Results: The right amygdala was significantly larger in unaffected BD offspring compared to BD offspring with psychiatric disorders and HC. Volumes of striatal, hippocampal, cingulate, and temporal regions were comparable across groups.

Discussion: The size of the amygdala may be a marker of disease susceptibility in offspring of BD parents. Longitudinal studies are needed to examine rates of conversion to BD as related to specific pre-morbid brain abnormalities.

Keywords: Amygdala; Bipolar disorder; Freesurfer; Offspring; Volume.

Figure 1

Least squares means of right amygdala volumes (mm3) with age, gender, ethnicity and ICV as covariates in healthy controls (HC), unaffected (UA) and affected offspring (AO-BD) (Panel A), and in AO-BD and offspring with other mood disorders (AO-Other) (Panel B). Vertical bars denote 95% confidence intervals. *p<.05.