The distinction between BD and DMDD does matter, but it is sometimes quite hard to draw a clear line – even for the experts. It can be easy to be frustrated with yourself as a clinician when you’re unable to come to a clear decision about the diagnosis. With mood disorders in children, however, it’s important not to attribute the field’s lack of clarity to your own lack of knowledge. In these difficult cases, it’s highly likely that even the experts would disagree. Making the distinction between bipolar disorder and DMDD becomes even more complex in the situation of “other specified bipolar and related disorders,” which allows for short or subsyndromal hypomanic episodes with major depression, hypomania without depression, or short-duration cyclothymia. These cases, formerly called “bipolar, not otherwise specified,” are more likely to progress to adult bipolar disorder I or II. DMDD, on the other hand, is more likely to progress to adult depression (Biol. Psychiatry 2006;60:991-7).
Why does the distinction matter? Because the treatment for bipolar disorder is likely to involve one of the traditional mood stabilizers or the second-generation antipsychotics that are Food and Drug Administration–approved for bipolar disorder along with family education and cognitive-behavioral therapy. However, there is no evidence at this time that the management of DMDD should consist of these same treatments. In fact, a trial of lithium for DMDD (actually, its research predecessor severe mood dysregulation) was negative (J. Child. Adolesc. Psychopharmacol. 2009;19:61-73). While we are still working out how to help children with DMDD, the current trials being done are examining the use of antidepressants and psychostimulants (either serially or in combination) along with family-based interventions similar to those used for ODD. These are tough cases, and frequently a consult with a child psychiatrist or psychologist will be helpful.
Dr. Althoff is an associate professor of psychiatry, psychology, and pediatrics at the University of Vermont, Burlington. He is director of the division of behavioral genetics and conducts research on the development of self-regulation in children. Dr. Althoff has received grants/research support from the National Institute of Mental Health, the National Institute of General Medical Sciences, the Research Center for Children, Youth, and Families, and the Klingenstein Third Generation Foundation, and honoraria from the Oakstone General Publishing for CME presentations. E-mail him at email@example.com.