Research findings suggest that there are unique neural mechanisms mediating face??”emotion processing deficits in patients with attention deficit/hyperactivity disorder (ADHD), bipolar disorder, and severe mood dysregulation.

Diagnosing these three psychiatric illnesses is difficult because deficits in emotion processing and hyperarousal symptoms are clinical features common to all three conditions, note Melissa Brotman (National Institute of Mental Health, Bethesda, Maryland, USA) and colleagues.

Evidence of unique neural mechanisms mediating face??”emotion processing deficits could therefore assist in the differential diagnosis of bipolar disorder, ADHD, and severe mood dysregulation in children, they say.

The researchers used functional magnetic resonance imaging (fMRI) to examine blood-oxygen-level-dependent (BOLD) signal in the amygdala of 43 children with bipolar disorder, 18 with nonirritable ADHD, and 29 children with chronic irritability known as severe mood dysregulation, and 37 mentally healthy children. The children were aged between 8 and 17 years.

During imaging, the children were shown pictures of adult faces, displaying neutral expressions. The children viewed the faces passively and were then asked to rate the perceived threat (how hostile is this face?) and subjective fear (how afraid are you of this face?) associated with the faces.

The results, published in the American Journal of Psychiatry, show that patients with bipolar disorder and those with severe mood dysregulation were more afraid of neutral faces than healthy individuals, while there was no difference for children with ADHD. There were no group differences with regard to hostility ratings.

Moreover, patients with severe mood dysregulation showed left amygdala hypoactivity when completing subjective fear ratings of neutral faces relative to mentally healthy children and those with bipolar disorder or ADHD.

In contrast, children with ADHD showed left amygdala hyperactivity relative to the other three groups when rating subjective fear of neutral faces.

Amygdala activity in children with bipolar disorder did not differ significantly from that in mentally healthy children.

“These findings suggest that there may be functional differences among ADHD, bipolar disorder, and severe mood dysregulation patients, despite the presence of overlapping behavioral deficits and clinical symptoms,” say Brotman et al.

In a related editorial, Mary Phillips, from University of Pittsburgh Medical Center in Pennsylvania, USA, said the findings “highlight the future promise of neuroimaging to identify biomarkers of psychiatric illnesses in youth.”

She added: “Further studies are clearly needed to elucidate whether functional abnormalities in key neural circuitry in emotion processing and emotion regulation, including not only the amygdala but also other neural regions interconnected with the amygdala, can accurately differentiate between bipolar disorder and other psychiatric illnesses in youth.”

MedWire (www.medwire-news.md) is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

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