Editorial: Defining the Clinical Boundary of Disruptive Mood Dysregulation Disorder Symptoms in Youth.

Disruptive mood dysregulation disorder (DMDD) is a novel diagnosis emerging from a continuing discourse on the best diagnostic home for children with severe, chronic irritability. DMDD emerged from a research diagnosis that was developed to test the hypothesis that severe, chronic irritability is a developmental phenotype of pediatric bipolar disorder.1 That is, such irritability is a phenomenon that emerges prior to a hypo/manic episode that defines bipolar disorder. For many, such irritability in conjunction with attention-deficit/hyperactivity disorder (ADHD) symptoms had been treated as a prodrome of bipolar disorder. Although this line of research did not establish a deterministic association between the DMDD syndrome and later bipolar disorder, it did provide guidance for assessing the risk of irritability for later bipolar disorder.2 Among the outcomes was the introduction of DMDD as a new diagnosis in DSM-5. It is defined by 2 core symptoms-temper outbursts and irritable/angry mood-the 2 major features of irritability. However, what qualifies as DMDD-level irritable mood and temper outbursts is unclear, and, unlike other mood disorders, no ancillary symptom criteria are available to establish a diagnosis of DMDD. Through the example of the relationship between DMDD and ODD, we will illustrate the clinical impact of this lack of clarity and describe the current efforts to establish a developmentally sensitive clinical nosology for irritability.