Mara Otten1, Martijn Meeter2. 1. Department of Cognitive Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081BT Amsterdam, The Netherlands. Electronic address: mara.otten@vu.nl. 2. Department of Cognitive Psychology, VU University Amsterdam, Van der Boechorststraat 1, 1081BT Amsterdam, The Netherlands.
Abstract
INTRODUCTION: Bipolar disorder (BD) is a psychiatric disorder accompanied by deficits in declarative memory. Given the importance of the hippocampus in declarative memory, it is not surprising that BD patients have been reported to show hippocampal abnormalities. OBJECTIVES: Review evidence about structural and functional hippocampal abnormalities in BD. METHODS: Systematic review of studies comparing BD patients and healthy controls with respect to hippocampal structure or function. RESULTS: Twenty-five studies were included, together involving 1043 patients, 21 of which compared patients to controls. Decrease in hippocampal volume was found in four of 18 studies using adult samples, and two of three samples using adolescents. Four studies revealed localized hippocampal deficits. Meta-analysis revealed a significant but small effect with lower hippocampal volumes when comparing all BD patients with controls. Lithium treatment was associated with larger hippocampal volumes across studies. The three functional studies yielded contradictory evidence. LIMITATIONS: Studies were only cross-sectional in nature and all used MRI or fMRI to investigate hippocampal volume or function. Heterogeneous patients groups and different methodologies for hippocampal segmentation, may have contributed to difficulties when comparing the different studies. CONCLUSIONS: There seems to be a small reduction in hippocampal volume in BD, which perhaps is more pronounced in early-onset BD and is counteracted by a neuroprotective effect of lithium treatment. However, how these structural abnormalities relate to functional deficits is largely unclear. Given the few functional neuroimaging studies and given the lack of congruence in these results, further investigation of especially hippocampal function in BD is recommended.
INTRODUCTION:Bipolar disorder (BD) is a psychiatric disorder accompanied by deficits in declarative memory. Given the importance of the hippocampus in declarative memory, it is not surprising that BDpatients have been reported to show hippocampal abnormalities. OBJECTIVES: Review evidence about structural and functional hippocampal abnormalities in BD. METHODS: Systematic review of studies comparing BDpatients and healthy controls with respect to hippocampal structure or function. RESULTS: Twenty-five studies were included, together involving 1043 patients, 21 of which compared patients to controls. Decrease in hippocampal volume was found in four of 18 studies using adult samples, and two of three samples using adolescents. Four studies revealed localized hippocampal deficits. Meta-analysis revealed a significant but small effect with lower hippocampal volumes when comparing all BDpatients with controls. Lithium treatment was associated with larger hippocampal volumes across studies. The three functional studies yielded contradictory evidence. LIMITATIONS: Studies were only cross-sectional in nature and all used MRI or fMRI to investigate hippocampal volume or function. Heterogeneous patients groups and different methodologies for hippocampal segmentation, may have contributed to difficulties when comparing the different studies. CONCLUSIONS: There seems to be a small reduction in hippocampal volume in BD, which perhaps is more pronounced in early-onset BD and is counteracted by a neuroprotective effect of lithium treatment. However, how these structural abnormalities relate to functional deficits is largely unclear. Given the few functional neuroimaging studies and given the lack of congruence in these results, further investigation of especially hippocampal function in BD is recommended.
Authors: Bo Cao; Isabelle E Bauer; Ajaykumar N Sharma; Benson Mwangi; Thomas Frazier; Luca Lavagnino; Giovana B Zunta-Soares; Consuelo Walss-Bass; David C Glahn; Flavio Kapczinski; David A Nielsen; Jair C Soares Journal: J Affect Disord Date: 2016-03-10 Impact factor: 4.839
Authors: Rachel A McKinney; Suzanne N Avery; Kristan Armstrong; Jennifer Urbano Blackford; Neil D Woodward; Stephan Heckers Journal: Psychiatry Res Date: 2020-10-11 Impact factor: 3.222