Disruptive Mood Dysregulation Disorder

Introduction

Irritability is a symptom, which is found in several pediatric psychiatric illnesses, from depression to bipolar disorder (BD) to oppositional defiant disorder (ODD). Until recently, it was not studied outside of these illnesses. However, the description of irritability in these illnesses does not capture the impairment that is caused by severe nonepisodic irritability. The increased incidence and prevalence of BD seems to be in some part driven by the need to recognize and treat nonepisodic irritability as it is severely debilitating. One of the most troublesome implications of diagnosing more and more children with BD is the increased use of antipsychotic medications as mood stabilizers. Given the potency of these agents, their potential for deleterious side effects and the widespread use of the medications in young children, there has been investigation into the prescribing trends in the United States.

Research aimed at elucidating the relationship between irritability and BD led to the definition of SMD, an illness defined for study protocols but not found in the DSM . The diagnostic criteria capture those patients who have chronic nonepisodic irritability and emotional reactivity. Longitudinal follow-up studies showed that patients with SMD did not have an increased incidence of mania compared with counterparts with narrowly defined BD. However, irritability does increase risk for anxiety, depression, and suicidality. The introduction of DMDD allows clinicians to target nonepisodic irritability and has spurred research to investigate novel interventions, which can alleviate symptoms and protect against long-term sequelae.

Disruptive mood dysregulation disorder (DMDD) is defined as severe nonepisodic (chronic) irritability and exaggerated emotional reactivity, which lasts for at least 12 months, with breaks no longer than 3 months, in children ages 6–18 years. Irritability is defined as intolerance of and excessive reactivity to negative emotional stimuli often resulting in anger, frustration, and aggression. Although aggression may stem from irritability, it is important to distinguish between them. Irritability is a trait, and aggression is a behavior. Traits are defined as being both stable and heritable. The heritability of irritability has been shown to be 0.3–0.4, and it is a trait that is stable over time.

Even mild irritability can disrupt daily functioning. Because of its shared presentation in BD, depression, and ODD, identification of the features of irritability, such as time course and severity, is integral in differentiating DMDD from other disorders. The heterogeneity in the presentation of irritability demonstrates that there are different mechanisms in these illnesses which can cause the phenotype. This is supported by the fact that some treatments for these illnesses are diametrically opposed.

Irritability is also one of the primary targets of treatment, as it is often the most debilitating aspect of those illnesses. Armed with the data from longitudinal studies of SMD, the development of DMDD was shaped by the hypothesis that the illness is more etiologically similar to depression, anxiety, and attention deficit hyperactivity disorder (ADHD). Convincing evidence from longitudinal and family aggregation studies of children diagnosed with DMDD supports this conceptualization. Thus, DMDD is listed under depressive disorders in Diagnostic and Statistical Manual of Mental Disorders , 5th ed. ( DSM-5 ), whereas symptoms of BD, such as manic and hypomanic episodes, are exclusionary criteria.

Because of the disorder’s new nosologic status, recommendations for treatment interventions are emerging. The body of evidence does reveal that treatment algorithms for disorders, which share biologic pathways, are relevant in treating DMDD. Further there are novel approaches, developed because of the understanding of the neurobiologic correlates of irritability , which are promising and have led to an improvement in functioning and altered circuitry.

Definition/Symptom Criteria

According to the DSM-5 , the following diagnostic criteria (see Tables 15.1 and 15.2 ) must occur for at least 12 months with no more than 3 months symptom-free. Diagnosis must be made between ages 6 and 18 years to accommodate the typical developmental trajectory of irritability. The onset of symptoms must occur before 10 years of age.

Prevalence/Epidemiology

DMDD occurs in 0.8–3.3% of the population. Affected children exhibit greater rates of service use, school suspension, social impairments, and poverty. There were no significant sex differences in 3-month prevalence rates in community samples, except that the number of settings in which symptoms were observed was higher in boys than in girls. However, prevalence for children in clinics has been predominantly male.

The frequency of tantrums and negative mood tends to decrease with age, aligning with developmental studies, suggesting that the peak of temper tantrums and irritability occurs during early childhood and then wanes in adolescence. Of those who met criteria for severe, chronic irritability, half no longer did so after 1 year. Although a community study of preschoolers aged 2–5 years had greater prevalence rates of DMDD symptoms than older children aged 9–17 years, the DSM-5 precludes diagnosis before age 6 years owing to concerns of pathologizing normal behavior. DMDD cooccurs with another disorder 62%–92% of the time, most often with depressive disorders and ODD.