One preliminary report suggests that SMD has a lifetime prevalence of 3.3% among those ages 9-19. Recent longitudinal studies further indicate that children with SMD have increased rates of adult mood and anxiety disorders, substance abuse, suicidality, and poorer overall functioning. Given this significant morbidity, it is essential that the investigators increase understanding of children with chronic irritability and affective instability. Impulsive aggression in childhood has been identified as a significant public health concern that cuts across currently defined diagnostic categories. These youth demonstrate increased difficulties with school adjustment, peer interactions, cognitive deficits, problem-solving, and physical abuse - a developmental trajectory predictive of significant adult dysfunction.