Objective: Irritability in children with autism spectrum disorder (ASD) is prominent and often leads to distress to both autistic children and their families. However, the nature of irritability in autism and the difference from nonautistic children have rarely been examined. This study aimed to investigate the clinical characteristics of irritability in autism, and to compare the symptom profiles with those of disruptive mood dysregulation disorder (DMDD) in nonautistic children. Methods: Fifty-six children aged 7-17 years (mean age 10.36 ± 3.05) were recruited into this study (21 with DMDD, 21 with high-functioning autism [hfASD], and 14 healthy volunteers [HV]). Their parents completed the Aberrant Behavior Checklist-Irritability (ABC-I) subscale and the Strengths and Difficulties Questionnaire (SDQ) parent report form. The ABC-I subscale was analyzed as a whole and broken into subsets (ABC-I-Irritability, ABC-I-Agitation, and ABC-I-Crying). The symptom profiles of irritability and the association with psychosocial difficulties were compared between groups. Results: The ABC-I-Irritability scores of children with hfASD closely matched to those of children with DMDD. In addition, both DMDD and hfASD groups could be differentiated from HV group in five of the six items except "depressed mood." However, in the ABC-I-Agitation scale, children with DMDD, but not hfASD, had higher scores in "Aggressive to other patients and staff" and "Stamps feet while banging objects or slamming doors" than HV. Regarding psychosocial outcomes, irritability in children with DMDD and hfASD were associated with emotional problems as measured by the SDQ. Moreover, irritability in DMDD was associated with conduct problems, and the hfASD group exhibited the similar trend. Conclusions: Symptom profiles of irritability and the associated emotional and conduct problems in children with hfASD were similar to those of DMDD in the nonautistic population. Future studies are warranted to explore the underlying neurophysiological mechanisms of irritability between autistic and nonautistic children for further insight into the nature of irritability in autism.
Keywords: Aberrant Behavior Checklist; Strengths and Difficulties Questionnaire; autism spectrum disorder; comorbidity; disruptive mood dysregulation disorder; irritability.