Editorial: White Matter Matters: Neurobiological Differences Between Pediatric Bipolar Disorder and Disruptive Mood Dysregulation Disorder

Think about this: Linke et al.¹ are publishing the "first" ever study using diffusion tensor imaging (DTI) in children with disruptive mood dysregulation disorder (DMDD). Child and adolescent psychiatrists know that these children are not new and are not uncommonly seen in both inpatient and outpatient mental health settings. So, why does the first paper examining the microstructural differences in white matter tracts in children with DMDD emerge in 2019? If you search PubMed using the key words "autism" and "diffusion tensor imaging" (as children with autistic symptoms have likely been around for as long as children with symptoms of dysregulation), you end up with 305 papers. So, what's the story? Was aberrant white matter microstructure never considered as a putative hypothesis for DMDD? Or did DMDD fall under a different name, and, as Shakespeare once wrote, "a rose by any other name would smell as sweet"? Or, in our loose psychiatric-based translation from Old English, "a pediatric bipolar child by any other name is just as dysregulated?" Indeed, DMDD has had a circuitous and somewhat shady history, with its roots in the name "pediatric bipolar disorder."² Because a number of long-term studies showed that few children with chronic irritable mood problems progressed to develop adult bipolar affective disorder (BPAD),³ DMDD emerged in the DSM-5.⁴.