[Author Affiliation]Daniel F. Connor. Department of Psychiatry, University of Connecticut School of Medicine, Farmington, Connecticut.Address correspondence to: Daniel F. Connor, MD, Department of Psychiatry/MC 1410, University of Connecticut School of Medicine, 263 Farmington Avenue, Farmington, CT 06030-1410, E-mail: dconnor@uchc.eduClinicians working in the mental health setting have long been challenged by children and adolescents with many different types of psychiatric disorders who are often referred for treatment because of frequent, intense, severe, and maladaptive impulsive aggression. This type of clinical presentation occurs commonly in every type of pediatric mental health treatment setting: Outpatient, inpatient, residential, and/or partial hospitalization. Impulsive aggression is often chronic, but waxes and wanes in response to multiple shifting internal and external factors, and may be extremely stressful for parents and other family members. Although normative in the young toddler and preschooler (the terrible twos), with development, the child begins to achieve emotional and behavioral competence and regulation such that by school entry aggression becomes increasingly verbal and not physical. With school entry, aggression is increasingly associated with understandable and recognizable antecedents, goals, and objectives.Maladaptive aggression is defined as behavior with intent to harm another person; is elicited by minimal or routine environmental cues; is less linked to recognizable and understandable social goals; is characterized by its explosive nature, high frequency rate, and severe intensity; and is associated with significant functional impairment for the child and the child's family (Connor 2002). Impulsive aggression is behavior that occurs rapidly without a delay (a short fuse) that would otherwise allow the child to consider an alternative and more adaptive response to frustration or perceived threat (Jensen et al. 2007). Impulsive aggression is driven by low frustration tolerance or fear of threat (Dodge and Coie 1987).Maladaptive and impulsive aggression in psychiatrically referred children and adolescents is common, denotes illness severity not illness specificity (Connor and McLaughlin 2006), and represents a significant public health problem with high societal costs (Foster and Jones 2005). Aggression is a major cause of referral to outpatient and inpatient child and adolescent psychiatry services (Bambauer and Connor 2005) and emergency psychiatric services (Gabel and Shindledecker 1991), predicts longer stays in psychiatric hospitals, and predicts rehospitalization in youth discharged from inpatient settings (Blader 2004). It is associated with child and adolescent psychiatry staff injury (Cunningham et al. 2003), is associated with off-label pediatric antipsychotic use (Olfson et al. 2015), and predicts combined pharmacotherapy (polypharmacy) use independently of diagnosis in referred children (Connor et al. 1997). Youth with moderate to severe impulsive aggression with and without comorbid attention-deficit/hyperactivity disorder (ADHD) are a major challenge for clinicians working in the clinical setting, as few evidence-based treatments are currently available that address these issues.Progress in developing effective treatments for impulsive aggression has been slowed by the multiple ways of clinically identifying and characterizing the aggressive child. Diagnostic and Statistical Manual of Mental Disorders, 5th ed. (DSM 5) diagnoses such as oppositional defiant disorder (temper tantrums), conduct disorder (physical aggression), bipolar disorder (aggression and irritability), intermittent explosive disorder (explosive aggression), and/or disruptive mood dysregulation disorder (irritability and temper tantrums) all may have aggression as part of their symptom criteria, yet are nosologically construed as separate and non-overlapping psychiatric diagnoses (American Psychiatric Association 2013). …