Amygdala activation linked to bipolar disorder risk
MedWire News: Individuals at risk for developing bipolar disorder may have increased activation in the left amygdala that suggests a heritable endophenotype, say UK researchers, who also found potential subclinical indicators of illness that are not linked to familial risk.
Previous functional imaging studies have revealed that bipolar disorder patients have abnormalities in the prefrontal cortex, striatum, and limbic regions, particularly the amygdala. Furthermore, there is a strong heritable component to bipolar disorder, with unaffected relatives displaying neurobiological abnormalities.
To investigate further, Heather Whalley and colleagues, from the University of Edinburgh, performed functional magnetic resonance imaging scans on 93 unaffected relatives of bipolar disorder patients and 70 healthy individuals while carrying out the Hayling sentence completion paradigm.
In addition, participants completed the Young Mania Rating Scale, the Hamilton Depression Rating Scale, and the Temperament Evaluation of Memphis, Pisa, Paris, and San Diego-autoquestionnaire (TEMPS-A).
Individuals at high risk for bipolar disorder had significantly greater depressive symptoms, and a trend for different levels of cyclothymia, compared with their healthy counterparts, reports the team in the journal Biological Psychiatry. No other significant differences in demographic or clinical characteristics were found between the two groups, however.
Increased activation was observed in the left amygdala in high-risk individuals compared with controls, which remained significant after taking into account age, gender, and intelligence quotient. There were no significant associations with depression and mania scores, or scores on the TEMPS-A.
The researchers found a significant association between depression scores and activation in the ventral striatum for sentence completion in both the high-risk and control groups. A similar association was recorded for cyclothymia and activation in ventral prefrontal regions.
They conclude: "These findings therefore provide evidence that genetic vulnerability to bipolar disorder may be inherited as a disruption in limbic processing, and subclinical features of the illness may also have a distinct biological basis."
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By Liam Davenport