In some, the problem is that their abnormal moods are primarily irritable, and they never get the elation that is most typical of the illness.
Others may experience elation, but only for hours at a time, rather than the four days required for hypomania, or the seven for mania.
In still other patients, the issue is distinguishing the impulsivity and agitation of bipolar disorder from disruptive behavioral disorders, such as those mentioned earlier: attention deficit hyperactivity disorder, and oppositional defiant disorder.
Ellen Leibenluft, a psychiatrist at the National Institute of Mental Health in Bethesda, Md., refers to this gray-area group as having "severe mood dysregulation," rather than bipolar disorder.
In last month's American Journal of Psychiatry, she and her colleagues compared rates of bipolar disorder in parents of children with bipolar disorder, and parents of children with severe mood dysregulation.
The rate in the former group was 18 times higher than that in the latter, suggesting that severe mood dysregulation may be a different animal than bipolar disorder.
What do children look like before they develop bipolar disorder? Liebenluft and colleagues reported last year that very few children with severe mood dysregulation develop bipolar disorder.
Our group at Johns Hopkins is part of a larger study examining adolescents whose parents have bipolar disorder, to determine whether there is a set of symptoms or illnesses that distinguish them, and whether there are factors or behaviors, such as drug and alcohol use, for example, that put them at greater risk of eventually developing bipolar disorder themselves.
Researchers will likely study this group's DNA to try to correlate genetic risk factors with patterns in the manifestation of illness.
The increase in the diagnosis of bipolar disorder in youth has, of course, led to increased prescribing of relevant medications, such as mood stabilizers and neuroleptics, for this group.
Another challenge we face is that little data currently exists on the effectiveness of these drugs in this age group.
One project, the Treatment of Early Age Mania study, being conducted at Johns Hopkins and other sites, including Washington University in St. Louis, is trying to help rectify this. The group aims to assess which medications are most effective in manic patients from age 6 to 15.
Their results should help us toward an increased level of confidence in prescribing decisions.
Dr. James Potash is an associate professor of psychiatry and co-director of the Mood Disorders Program (http://www.hopkinsmedicine.org/moods) at the Johns Hopkins School of Medicine in Baltimore, Md. If you have questions or comments, please e-mail at firstname.lastname@example.org. To participate in our studies, call 1-877-MOODS-JH.