Abstract
A major controversy in child psychiatry is whether bipolar disorder (BD) presents in children as severe, non-episodic irritability (operationalized here as severe mood dysregulation, SMD), rather than with manic episodes as in adults. Both classic, episodic BD and SMD are severe mood disorders characterized by deficits in processing emotional stimuli. Neuroimaging techniques can be used to test whether the pathophysiology mediating these deficits are similar across the two phenotypes. Amygdala dysfunction during face emotion processing is well-documented in BD, but little is known about amygdala dysfunction in chronically irritable youth. We compared neural activation in SMD (n = 19), BD (n = 19), and healthy volunteer (HV; n = 15) youths during an implicit face-emotion processing task with angry, fearful and neutral expressions. In the right amygdala, both SMD and BD exhibited greater activity across all expressions than HV. However, SMD and BD differed from each other and HV in posterior cingulate cortex, posterior insula, and inferior parietal lobe. In these regions, only SMD showed deactivation in response to fearful expressions, whereas only BD showed deactivation in response to angry expressions. Thus, during implicit face emotion processing, youth with BD and those with SMD exhibit similar amygdala dysfunction but different abnormalities in regions involved in information monitoring and integration.
Highlights
The diagnosis of bipolar disorder (BD) is being assigned to youth with increasing frequency (Moreno et al, 2007)
We focused on face emotion processing because both pediatric BD and severe mood dysregulation (SMD) youth manifest behavioral deficits in this domain; both patient groups misidentify facial emotions, including happy, sad, fearful and angry expressions (Guyer et al, 2007; McClure et al, 2005; Rich et al, 2008; Schenkel et al, 2007)
The current findings suggest that emotion processing deficits in BD and SMD are associated with abnormal activity in some of the neural regions that comprise the default mode network
Summary
The diagnosis of bipolar disorder (BD) is being assigned to youth with increasing frequency (Moreno et al, 2007) This upsurge may reflect the controversial view that mania manifests in youth as severe, non-episodic irritability (Leibenluft et al, 2003) rather than with distinct manic episodes, as in adults. To facilitate research on this question, we operationalized severe, chronic irritability in youth as “severe mood dysregulation (SMD)” to test whether it is distinct from episodic BD (Leibenluft et al, 2003) This question is important because severe irritability occurs much more commonly in youth than classic, episodic mania (Brotman et al, 2006), and because the diagnostic formulation has treatment implications (Leibenluft, 2011). It is important to complement research based on clinical measures with pathophysiological comparisons of the two clinical syndromes to ascertain the extent to which they share common neural deficits and are likely to respond to similar therapeutic interventions
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