Ellen Leibenluft, M.D. published an article in the February 2011 issue of the American Journal of Psychiatry (ajp.psychiatryonline.org) entitled Severe Mood Dysregulation, Irritability(SMD), and the Diagnostic Boundaries of Bipolar Disorder in Youths. As the title suggests, the hallmark feature of this disorder is irritability. In this article she is distinguishing between clearly bipolar patients and those where the situation is uncertain and is characterized by severe and chronic irritability with frequent (three or more times per week) emotional outbursts causing consequent disruptions at home, disciplinary actions at school, impaired social functioning and parents who often report that they feel that they are walking on eggshell around these children. These are not episodic, persist for more than one year and start before 12 years of age. These youths respond inappropriately to frustration and have hyperarousal symptoms of racing thoughts, insomnia, agitation and distractibility but lack the episodic nature of bipolar disorder. They are clearly anxious and depressed. This condition is also common with estimates of a lifetime prevalence of 3.2 percent.
Yet how should they be diagnosed? A diagnosis of bipolar disorder is inaccurate because of the non-episodic course. ADHD does not encapsulate the anxiety and depression. If we examine longitudinal data from clinical and community samples there is evidence of differentiation between SMD and bipolar disorder. Children with SMD appear to be at risk for unipolar depressive disorders and anxiety disorders as adults but not for bipolar disorder. Youths with SMD also have lower familial rates of bipolar disorder than do those with bipolar disorder. While youths of both groups have deficits in face emotion labeling and demonstrate more frustration than normally developing children, the underlying brain mechanisms are different in the two groups. Interestingly, children with ADHD, anxiety disorders, major depressive disorder, or conduct disorder do not share deficit in facial-emotion recognition. Leibenluft noted that fMRI during face-emotion testing shows neural activity in the amygdala differs between youths with SMD and those with bipolar disorder. Youths with SMD demonstrated lower amygdala activity while rating fear when compared to youths with bipolar disorder, non-irritable youth with ADHD, and healthy controls.
This diagnostic category will be evaluated in the upcoming trials for DSM-V in which I will be a participant.