Cyclothymic disorder in youth: why is it overlooked, what do we know and where is the field headed?

Cyclothymic disorder is a chronic and impairing subtype of bipolar disorder, largely neglected in pediatric research. Consequently, it is rarely diagnosed clinically despite potentially being the most prevalent form of bipolar disorder. Lack of attention has added to confusion about the diagnosis and clinical presentation of cyclothymic disorder. In pediatric studies, cyclothymic disorder is commonly grouped with 'subthreshold' presentations of bipolar disorder under the undifferentiated label 'bipolar disorder not otherwise specified'. However, research indicates that cyclothymic disorder can be reliably distinguished from the other forms of bipolar disorder and from other childhood disorders. Importantly, cyclothymic disorder may be a diathesis for more acute presentations of bipolar disorder, warranting a prominent role in dimensional models of mood and psychopathology. Current evidence suggests that cyclothymic disorder has the potential to make unique contributions to our understanding of the risk factors and outcomes associated with bipolar disorder. This potential has yet to be fully realized, limiting our knowledge and ability to intervene in a meaningful way with youth who are exhibiting symptoms of a major mood disorder. Including cyclothymic disorder in future research studies of children - particularly longitudinal outcome studies - is essential for understanding the developmental trajectory of bipolar spectrum disorders and learning how to accurately diagnosis and treat the full spectrum of bipolar disorders.