Are youths with disruptive mood dysregulation disorder different from youths with major depressive disorder or persistent depressive disorder?

Background: Although the disruptive mood dysregulation disorder (DMDD) was included in the depressive disorders (DD) section of the DSM-5, common and distinctive features between DMDD and the pre-existing DD (i.e., major depressive disorder, MDD, and persistent depressive disorder, PDD) received little scrutiny. Methods: Youths consecutively assessed as outpatients at two Canadian mood clinics over four years were included in the study (n = 163; mean age:13.4 +/- 0.3; range:7-17). After controlling for inter-rater agreement, data were extracted from medical charts, using previously validated chart-review instruments. Results: Twenty-two percent of youths were diagnosed with DMDD (compared to 36% for MDD and 25% for PDD), with substantial overlap between the three disorders. Youths with DMDD were more likely to have a comorbid non-depressive psychiatric disorder - particularly attention deficit hyperactivity disorder, odds ratio (OR= 3.9), disruptive, impulse-control and conduct disorder (OR= 3.0) or trauma- and stressor-related disorder (OR = 2.5). Youths with DMDD did not differ with regard to the level of global functioning, but reported more school and peer-relationship difficulties compared to MDD and/or PDD. The vulnerability factors associated with mood disorders (i.e., history of parental depression and adverse life events) were found at a comparable frequency across the three groups. Limitations: The retrospective design and the selection bias for mood disordered patients restricted the generalizability of the results. Conclusions: Youths with DMDD share several clinical features with youths with MDD and PDD. Further studies are required to determine the developmental trajectories and the benefits of expanding pharmacotherapy for DD to DMDD.