Examining the proposed disruptive mood dysregulation disorder diagnosis in children in the Longitudinal Assessment of Manic Symptoms Study.

Irritable mood and temper outbursts are common in youth referred for psychiatric treatment.1,2 They are also the core features of the proposed diagnosis disruptive mood dysregulation disorder (DMDD) in DSM-5.3 DMDD is characterized primarily by frequent, severe, recurrent temper outbursts and chronically irritable and/or angry mood, both of which must be present for at least a year. The DSM-5 Work Groups raised concerns that many youth with severe, nonepisodic irritable mood are inappropriately diagnosed with bipolar disorder.4 The DMDD diagnosis was constructed to capture the phenomenology of youth with severe, chronic irritability, with the goal of reducing the chance that youth with this phenotype would receive a bipolar diagnosis. The DSM-5 Work Groups note that there is currently relatively limited research to support the DMDD diagnosis.4 Most available studies focus on an overlapping but not identical construct called severe mood dysregulation (SMD). SMD includes the core criteria of DMDD, but also requires symptoms of chronic hyperarousal such as insomnia, agitation, distractibility, racing thoughts, flight of ideas, pressured speech, and intrusiveness.5 Published research on SMD has primarily been from a carefully phenotyped cohort of 146 youth referred to the National Institute of Mental Health (NIMH) Intramural Program.6 The youth with SMD were predominantly male (66%) and had high lifetime rates of attention-deficit/hyperactivity disorder (ADHD; 85%), oppositional defiant disorder (86%), and anxiety disorders (58%). About 16% met lifetime criteria for major depressive disorder (MDD). The youth with SMD were shown to be different from youth with a specified phenotype of bipolar I disorder (requiring distinct episodes of manic symptoms, including either elated mood or grandiosity) on a number of domains, including lower familial rates of bipolar disorder, lower onset rates of manic and hypomanic episodes over prospective follow-up, and differences on several neuropsychological domains and measures of brain structure and functioning.6 Other studies relevant to the SMD/DMDD phenotype have been post hoc analyses of large datasets in which a retrospective diagnosis of SMD was derived from the existing phenotypic variables. In the Great Smoky Mountains Study, 1.8% of the sample met SMD criteria with severe functional impairment, which made it much more common than bipolar disorder (0.1% of the sample).7 The severely impaired SMD youth from this community sample were predominantly male (66%), but differed from those in the NIMH studies, as only about 32% met criteria for ADHD; 42%, for oppositional defiant disorder; and 21%, for any anxiety disorder. In addition, there was very little longitudinal stability of the SMD diagnosis (83% met SMD criteria at only 1 wave). A retrospective SMD diagnosis was applied to 4 large aggregated community samples and 2 large clinical samples, which were assessed using the NIMH Diagnostic Interview Schedule-IV.6 Preliminary analyses indicated that in the community samples, 15% of youth with oppositional defiant disorder met SMD criteria, as did about 25% of the youth with oppositional defiant disorder in the clinical samples. Additional data specific to the DMDD diagnosis are needed; however, given the time constraints involved with the release of the upcoming DSM-5, carefully performed prospective studies are not possible. One way to evaluate DMDD is to take data from existing cohorts and retrospectively construct a DMDD diagnosis, similar to what was done for SMD. The Longitudinal Assessment of Manic Symptoms (LAMS) study is one source that can provide suitable data, as participants were sampled from all children presenting for new evaluation at 9 different university-affiliated clinics and were carefully assessed using semistructured interviews. In order to evaluate the validity of the DMDD diagnosis, it is useful to keep in mind the 5 phases of systematic study proposed by Robins and Guze8 that are necessary to validate a particular diagnostic classification in psychiatry. Using the LAMS cohort, we can provide relevant data on 4 of these phases: (1) clinical description, (2) delimitation from other disorders, (3) follow-up study, and (4) family study. In this article, we examine the clinical phenomenology of LAMS participants who met a DMDD diagnostic phenotype at intake and evaluate whether the DMDD phenotype can be delimited from other diagnoses, is stable over a 2-year follow-up period, and predicts new onset of DSM-IV diagnoses. Lastly, we assess the association of the DMDD phenotype with parental history of different psychiatric disorders.