Researchers from Bradley Hospital and The Warren Alpert Medical School of Brown University suggest that irritability should be considered a vital symptom when diagnosing bipolar disorder in kids.
They say a small percentage of children with bipolar disorder experience manic episodes without extreme elation - one of the hallmarks of the disorder - and are diagnosed based on irritable mood alone.
"Diagnosing children with bipolar disorder is challenging. One of the chief controversies is whether irritability should be included among the criteria for this diagnosis because it can also overlap with a number of other psychiatric disorders, such as attention deficit hyperactivity disorder," said Dr Jeffrey Hunt, a child psychiatrist and training director at Bradley Hospital.
"Our findings confirm that while irritable-only mania is uncommon, it does exist - particularly in younger children - and should be considered in a bipolar diagnosis," he added.
During the study, the research team studied 361 children between the ages of 7 and 17 with bipolar disorder
They quantified the frequency and severity of manic symptoms of each participant, including whether irritability and elation were present.
The group was then reclassified into three subgroups: elation-only, irritable-only and both elated and irritable.
The study showed that approximately 10 percent of children fell into the irritable-only category, while elated-only constituted about 15 percent.
Moreover, nearly three-quarters experienced both elation and irritability. The irritable-only participants were significantly younger in age.
"The fact that the irritable-only and elation-only subgroup had similar clinical characteristics and family histories of bipolar disorder provides support for continuing to consider episodic irritability in the diagnosis of pediatric bipolar disorder," said Hunt.
The study appears in Journal of the American Academy of Child and Adolescent Psychiatry.