Researchers at the National Institute of Mental Health (NIMH) have discovered why children with bipolar disorder tend to be more aggressive and irritable and have poorer social skills than healthy children.
It seems that youths with bipolar disorder misread facial expressions as hostile and show heightened neural reactions when they focus on emotional aspects of neutral faces.
The study provides some of the first clues to the underlying workings of the episodes of mania and depression that disrupt friendships, school, and family life in up to one percent of children.
This misinterpretation say the researchers could explain the mania and depression that affects many children with bipolar disorder.
By using functional Magnetic Resonance Imaging (MRI) the researchers were able to measure the brain activity in a group of 22 bipolar children and 21 healthy children.
The children were asked to rate the hostility of a neutral facial expression versus a non-emotional feature and the researchers discovered that the left amygdala which registers fear in the brain, reacted more in children with bipolar disorder and the children with bipolar disorder could see emotion where the others couldn't.
Dr. Ellen Leibenluft of the NIMH's Mood and Anxiety Disorders Program says that since children seem to have a more severe form of the disorder, they may provide a clearer window into the underlying illness process than adult onset cases.
She says the results also suggest that bipolar disorder possibly stems from an impaired development of specific brain circuits, as is thought to occur in schizophrenia and other mental illnesses.
The researchers also found that other areas of the brain related to emotions, including the nucleus accumbens, putamen, and left prefrontal cortex, also showed higher activity levels in the bipolar subjects when they considered a face to be hostile.
Activity was no different between bipolar and healthy children when rating non-emotional features, which confirms that the differences between the groups of children are specifically related to emotional processes.
NIMH director Dr. Thomas Insel suggests that finding a brain imaging trait may be more selective than current clinical criteria, and might help refine the definition of pediatric bipolar disorder.
The researchers are now doing a follow up with imaging studies of children with bipolar spectrum disorders and healthy children who are at genetic risk for developing the disorder, to see if they also have the same amygdala over-activation.
Magnetic Resonance Imaging (MRI) studies have shown that, unlike in adults with the illness, the amygdala is consistently smaller in bipolar children than in healthy age-mates.
Also, the NIMH researchers had found earlier that bipolar children falter at identifying facial emotion and have difficulty regulating their attention when frustrated.
To learn more on bipolar disorder refer to the U.S. National Institute of Mental Health.
The research is published in the current issue of Proceedings of the National Academy of Sciences.