Possible neurobiological markers of bipolar disorder identified
MedWire News: A systematic review and meta-analysis of published studies has identified specific functional and structural brain abnormalities that may be possible neurobiological markers for bipolar disorder.
"Bipolar disorder is often misdiagnosed or tardily detected, leading to inadequate treatment and devastating consequences," comment Michèle Wessa (Central Institute of Mental Health, Mannheim, Germany) and team in the Journal of Affective Disorders.
"The identification of objective biomarkers, such as functional and structural brain abnormalities, of bipolar disorder might improve diagnosis and help elucidate its pathophysiology," they add.
The researchers therefore searched the literature for relevant functional neuroimaging studies related to emotional processing and structural whole-brain neuroimaging studies published up to September 2009.
In total, 13 functional magnetic resonance imaging studies, involving 156 bipolar disorder patients and 164 mentally healthy controls, and 15 structural imaging studies using whole-brain voxel-based morphometry, involving 443 bipolar disorder patients and 551 mentally healthy controls, were include in the final meta-analyses.
Analysis of the pooled data revealed that, compared with controls, patients with bipolar disorder had decreased activation and/or reduction in gray matter volume in the right inferior frontal gyrus, the right superior frontal gyrus, the anterior cingulate, and the precuneus.
This represents a cortical-cognitive brain network that has been associated with the regulation of emotions, the researchers note.
In contrast, patients with bipolar disorder showed increased activation in ventral-limbic brain structures (the parahippocampal gyrus and the amygdala) compared with controls.
These brain regions are known to mediate the experience of emotions and generation of emotional responses, observes the team.
Wessa et al conclude: "These results support and refine previously proposed neurobiological models of the disorder and suggest that an imbalance between cortical-cognitive and limbic brain networks may serve as a neurobiological marker of bipolar disorder."
They add: "The significance of the potential biomarkers identified by the present meta-analyses and their specificity particularly relative to unipolar depression as well as their predictive value for the diagnosis of bipolar disorder need to be evaluated and confirmed by further studies."
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By Mark Cowen