Fig. 1 Top–down view of conduct disorders. (A) Conduct disorders according to DSM-IV criteria. (26) Conduct disorders can be suspected when a child displays a repetitive and persistent pattern of serious aggressive or nonaggressive misbehaviours against people, animals or property that may be characterized as belligerent, destructive, threatening, physically cruel, deceitful, disobedient or dishonest. A diagnosis of conduct disorder can be established by the presence of 3 (or more) of the included criteria in the past 12 months, with at least 1 criterion present in the past 6 months and with the disturbance in behaviour causing clinically significant impairment in social, academic or occupational functioning. (B) Key brain structures in the circuitry that controls emotion: (i) OPFC in green and the VMPFC in red, (ii) DLPFC, (iii) amygdala and (iv) ACG. Each of these interconnected structures plays a role in different aspects of emotion regulation, and abnormalities in one or more of these regions or in the interconnections among them are associated with failures of emotion regulation and also increased propensity for impulsive aggression and violence. (Davidson RJ, Putnam KM, Larson CL. Dysfunction in the neural circuitry of emotion regulation–a possible prelude to violence. Science 2000;289:591–4. (27) Reprinted with permission from AAAS.) (C) Schematic model of one way in which developmental 5-HT disturbances may affect the neural circuitry regulating emotion, largely based on some of the reported effects of 5-HT transporter polymorphisms on the electrophysiology of the circuit. (Hariri AR, Holmes A. Genetics of emotional regulation: the role of the serotonin transporter in neural function. Trends Cogn Sci 2006;10:182–91. (28) ©2006, with permission from Elsevier.) 5-HT = serotonin; ACG = anterior cingulate gyrus; DLPFC = dorsolateral prefrontal cortex; OPFC = orbital prefrontal cortex; PFC = prefrontal cortex; VMPFC = ventromedial prefrontal cortex.