DMDD is a depressive disorder that was added to the Diagnostic and Statistical Manual of Mental Disorders (DSM), Fifth edition in 2013. Before DMDD was added to the DSM, researchers noticed that bipolar disorder (another disorder in the DSM) was being diagnosed for young children at alarming rates (APA, 2013). Researchers also noted that many children being diagnosed with bipolar were irritable all the time. Bipolar disorder is marked by episodic conditions (which means that a person diagnosed with bipolar disorder may experience a change in mood or energy for some period of time) (APA, 2013). As bipolar is a lifelong disorder, children being diagnosed with bipolar disorder might be exposed to lifelong medication (Marguiles, Weintraub, Basile, Grover & Carlson, 2012). Researchers have found that children with DMDD develop symptoms of depression as they age, as opposed to symptoms of bipolar (Paris, 2015).
At one point, publishers of the DSM considered using the term "temper dysregulation disorder" but worried that it might be confused with temper tantrums and changed the name to "disruptive mood dysregulation disorder" (Paris, 2015).
American Psychiatric Association. (2013). Diagnostic and statistical manual of mental disorders: DSM-5. Washington, D.C: American Psychiatric Association.
Margulies, D. M., Weintraub, S., Basile, J., Grover, P. J., & Carlson, G. A. (2012). Will disruptive mood dysregulation disorder reduce false diagnosis of bipolar disorder in children?. Bipolar Disorders, 14(5), 488-496. doi:10.1111/j.1399-5618.2012.01029.xi
Paris, Joel. (2015). The intelligent clinician's guide to the DSM-5. New York, N.Y: Oxford University Press.