Objective: Researchers disagree as to whether irritability is a diagnostic indicator for pediatric mania in bipolar disorder. The authors compared the behavioral and psychophysiological correlates of irritability among children with severe mood dysregulation (i.e., nonepisodic irritability and hyperarousal without episodes of euphoric mood) and narrow-phenotype bipolar disorder (i.e., a history of at least one manic or hypomanic episode with euphoric mood) as well as those with no diagnosis (i.e., healthy comparison children).
Method: Subjects with severe mood dysregulation (N=21) or narrow-phenotype bipolar disorder (N=35) and comparison subjects (N=26) completed the affective Posner task, an attentional task that manipulated emotional demands and induced frustration. Mood response, behavior (reaction time and accuracy), and brain activity (event-related potentials) were measured.
Results: The severe mood dysregulation and narrow-phenotype bipolar disorder groups both reported significantly more arousal than comparison subjects during frustration, but behavioral and psychophysiological performance differed between the patient groups. In the frustration condition, children with narrow-phenotype bipolar disorder had lower P3 amplitude than children with severe mood dysregulation or comparison subjects, reflecting impairments in executive attention. Regardless of emotional context, children with severe mood dysregulation had lower N1 event-related potential amplitude than comparison subjects or children with narrow-phenotype bipolar disorder, reflecting impairments in the initial stages of attention. Post hoc analyses demonstrated that the N1 deficit in children with severe mood dysregulation is associated with oppositional defiant disorder symptom severity.
Conclusions: Results indicate that while irritability is an important feature of severe mood dysregulation and narrow-phenotype bipolar disorder, the pathophysiology of irritability may differ among the groups and is influenced by oppositional defiant disorder severity.