Disruptive mood dysregulation disorder (DMDD) is a mood disorder diagnosed in children and adolescents who experience severe, non-episodic, persistent irritability or negative mood interspersed between episodes of extreme anger outbursts. This irritability is often expressed as outbursts disproportionate to the inciting situation, developmentally inappropriate for the child’s age, and must be evident for a period of at least one year. The diagnosis of DMDD was introduced to distinctly capture youth with irritable but non-cyclical moods so as to avoid misdiagnosis and overtreatment for bipolar disorder.

Insights into the pathophysiology of DMDD borrow from its historical (but not identical) counterpart, severe mood dysregulation (SMD). Similar to DMDD, SMD was introduced as a means to recognize children with severe non-episodic irritability but not bipolar disorder. However, SMD differed from DMDD in that it included persistently depressed mood, could have an onset up to age 12 (as opposed to age 10 in DMDD), and required the presence of symptoms of hyperarousal such as racing thoughts, insomnia, or pressured speech.

One theory is that children with DMDD have impaired identification of and impaired emotional regulation in response to perceived negative affect. Negative emotions may be over-identified —including in neutral faces—and responded to with greater reactivity or aggression than in healthy children.

Another theory is that DMDD arises from an impairment in reward-based learning. Youth with SMD display impaired learning from “frustration” stimuli; this means that when they are denied a reward while using a particular strategy during an assigned task, they find it harder to switch strategies in order to receive the reward than healthy youth. Youth with SMD (and presumably DMDD) may also experience greater frustration while performing these tests. Overall, this indicates a potentially enhanced sensitivity to losses in youth with DMDD. The manifestation is thus the externalization of unpleasant emotions.

As mentioned previously, DMDD was introduced as a diagnosis to prevent the overdiagnosis of bipolar disorder in children. This was done so prior to conducting any validity studies, leading to concerns about the integrity of DMDD as a unique diagnosis. These concerns are substantiated by the noticeable overlap between DMDD and other conditions such as oppositional defiant disorder (ODD) and attention-deficit hyperactivity disorder (ADHD). While the existence of DMDD as a diagnostic entity may indeed prevent the overdiagnosis of bipolar disorders, their overtreatment, and resultant unnecessary suffering from drug side effects, its validity as a unique diagnostic entity and a standardized treatment protocol remain to be ascertained in an evidence-based manner.