Neuropsychological profile differences between children with disruptive mood dysregulation disorder (DMDD) and attention-deficit/hyperactivity disorder (ADHD): a preliminary study

Abstract

Objectives: Disruptive mood dysregulation disorder (DMDD), characterized by severe irritability, and ADHD are highly comorbid. Clinical observation suggests that patients with DMDD have greater impairment in functioning at school. We compared the neuropsychological assessment scores across three groups of participants to test whether any cognitive differences exist among children with ADHD, DMDD and healthy control (HC) subjects. Methods: The study sample group consisted of 43 participants (14 DMDD, 14 ADHD and 15 age-matched HC, mean age = 9.51; SD = 2.10). All the subjects diagnosed with DMDD had comorbid ADHD. Subjects underwent extensive diagnostic measures including Kiddie Schedule for Affective Disorders and Schizophrenia (K-SADS). We applied the following tests: trail making test (TMT), symbol cancellation task (SCT), single letter cancellation task (SLCT), digit span learning (DSL), benton judgment of line orientation (JLO), Rey-Osterrieth complex figure test (CFT), letter and symbol cancellation test (LCT, SCT), Stroop color word (TBAG), and Wisconsin card sorting test (WCST). Results: There were statistically significant differences between these three groups on the TMS, F (2,41) = 5.270, p = 0.009, structured SLCT, F (2,41) = 3.376, p = 0.044, unstructured SLCT, F (2,41) = 5.142, p = 0.010, unstructured SCT, F (2,41) = 5.282, p = 0.009, the ROCFT, F (2,40) = 6.622, p = 0.003, the ROCFT: delayed recall condition score, F (2,40) = 3.647, p = 0.035), the ROCFT: delayed condition time, F (2,40) = 9.195, p = 0.001), Stroop test: incongruent color words condition, F (2,40) = 4.522, p = 0.017), Stroop test: naming the color of random words condition, F (2,40) = 3.647, p = 0.035). Post hoc analyses revealed little difference between ADHD and ADHD and DMDD groups except for the TMT. Conclusions: Neuropsychological properties for children with DMDD are very similar to those of ADHD. Selective and sustained attentional impairment, working memory, and set shifting difficulties are prominent in both ADHD and DMDD. Although results did not yield a significant difference, we observed more impaired performance in all tests, likely due to greater impulsivity and poorer frustration tolerance. Larger sample size is required to confirm this notion.