Work

Hippocampal morphology in lithium and non‐lithium‐treated bipolar I disorder patients, non‐bipolar co‐twins, and control twins

Year: 2011

Type: article

Abstract: BACKGROUND: Bipolar I disorder is a highly heritable psychiatric illness with undetermined predisposing genetic and environmental risk factors. We examined familial contributions to hippocampal morphology in bipolar disorder, using a population-based twin cohort design. METHODS: We acquired high-resolution brain MRI scans from 18 adult patients with bipolar I disorder [BPI; mean age 45.6 ± 8.69 (SD); 10 lithium-treated], 14 non-bipolar co-twins, and 32 demographically matched healthy comparison twins. We used three-dimensional radial distance mapping techniques to visualize hippocampal shape differences between groups. RESULTS: Lithium-treated BPI patients had significantly larger global hippocampal volume compared to both healthy controls (9%) and non-bipolar co-twins (12%), and trend-level larger volumes relative to non-lithium-treated BPI patients (8%). In contrast, hippocampal volumes in non-lithium-treated BPI patients did not differ from those of non-bipolar co-twins and control twins. 3D surface maps revealed thicker hippocampi in lithium-treated BPI probands compared with control twins across the entire anterior-to-posterior extent of the cornu ammonis (CA1 and 2) regions, and the anterior part of the subiculum. Unexpectedly, co-twins also showed significantly thicker hippocampi compared with control twins in regions that partially overlapped those showing effects in the lithium treated BPI probands. CONCLUSIONS: These findings suggest that regionally thickened hippocampi in bipolar I disorder may be partly due to familial factors and partly due to lithium-induced neurotrophy, neurogenesis, or neuroprotection. Unlike schizophrenia, hippocampal alterations in co-twins of bipolar I disorder probands are likely to manifest as subtle volume excess rather than deficit, perhaps indicating protective rather than risk effects.

Source: Human Brain Mapping

DOI: 10.1002/hbm.21239