title: Hippocampal morphology in lithium and non-lithium-treated bipolar I disorder patients, non-bipolar co-twins, and control twins.
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.
authors: Department of Psychiatry and Human Behavior, UCI, Irvine, California 92617, USA. tvanerp@uci.edu
authors: Theo G M
authors: TG
authors: van Erp
authors: Paul M
authors: PM
authors: Thompson
authors: Tuula
authors: T
authors: Kieseppä
authors: Carrie E
authors: CE
authors: Bearden
authors: Alexandria C
authors: AC
authors: Marino
authors: Gil D
authors: GD
authors: Hoftman
authors: Jari
authors: J
authors: Haukka
authors: Timo
authors: T
authors: Partonen
authors: Matti
authors: M
authors: Huttunen
authors: Jaakko
authors: J
authors: Kaprio
authors: Jouko
authors: J
authors: Lönnqvist
authors: Veli-Pekka
authors: VP
authors: Poutanen
authors: Arthur W
authors: AW
authors: Toga
authors: Tyrone D
authors: TD
authors: Cannon
mesh_terms: D000328:Adult; D018692:Antimanic Agents / Q000627:therapeutic use*; D001714:Bipolar Disorder / Q000188:drug therapy* / Q000473:pathology*; D005260:Female; D006624:Hippocampus / Q000187:drug effects* / Q000473:pathology*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted; D021621:Imaging, Three-Dimensional; D018020:Lithium Compounds / Q000627:therapeutic use*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged
chemical_list: D018692:Antimanic Agents; D018020:Lithium Compounds