Affective or impulsive aggression refers to dyscontrolled reactions, which have the potential or the intent to hurt others, that occur upon exposure to events perceived as noxious. The provocations are usually things that one might agree are annoyances but within a level of intensity that most other children handle with composure. Triggers may appear quite trivial, such as not getting the right cereal for breakfast. Directions to comply with an adult request or the need to end a preferred activity to transition to something else are very frequent antecedents to full-blown rage episodes. Hitting, kicking, destruction of property, and self-abusive behavior are common. A verbal onslaught of screaming, vulgarity, threats, and hurtful insults often provides soundtrack. Since the behavior is most often reactive and nearly instantaneous, it tends to be overt and unplanned. These events can also show a self-defeating character. That is, youngsters in their explosive rage may end up hurting themselves by, for instance, punching walls or glass, damaging their own prized possessions, or escalating when it is obvious, or should be, that doing so only worsens their plight. They may go after people much larger and stronger than themselves. A few children do regain composure when placated, but it is also common for these outbursts, once kindled, to have to run their course before the child regains control. The onset of these difficulties is most often in early childhood, especially among boys, and their risk for persistence into adulthood is great (11,33,34).

Proactive or instrumental aggression includes assaultive or coercive behavior purposefully used to achieve a goal such as material goods or social status. Willful property destruction is also included by some. Descriptions of proactive/instrumental aggression sometimes liken it to hunting, but for many species predation and intraspecific aggression have quite different underpinnings and phenomenology (35). A few features of proactive aggression make plain that the actor is in control. For instance, proactive aggression stops once the goal is achieved or when it becomes clear that it has become unobtainable. Victims are chosen to make success likely. The aggressor may take protective measures to avoid getting hurt and evasive action to avoid apprehension. While planning and premeditation are certainly consistent with proactive aggressive behavior, it is probably not a requirement. A number of “acquisitive” violent acts, such as certain robberies and sexual assaults, are often opportunistic and not necessarily performed with much forethought.

Among youth whose aggressive behavior is principally of the proactive/instrumental type, we can also discriminate two important subgroups.

Frick and colleagues (54) reported that specific forms of antisocial behavior tend to aggregate. Put another way, antisocial youngsters seem to display some degree of “specialization.”
Their analysis identified two relatively independent dimensions, which, if dichotomized and crossed, yields quadrants that can categorize most antisocial behavior. One continuum is an overt–covert dimension and the other a destructive–nondestructive dimension. If the destructive dimension roughly corresponds to aggressive behavior, the result is that a certain number of youngsters show mainly overtly aggressive behavior, while another group’s aggressive misconduct is chiefly covert. Overt aggression, as mentioned earlier, is confrontative and may or may not be affectively charged. Covert aggression involves property vandalism, arson, and other damage that may well lead to the physical injury of others in addition to the obvious economic harms. The planning and effort needed to conceal one’s involvement indicates that covert aggressive behavior is volitional.

In this framework, overt aggression is motivated largely by interpersonal conflict, anger, or to establish dominance (55). Meanwhile, covert misconduct serves mostly acquisitive purposes, is attended by neutral affect, and is thought to be on the whole less violent, although it is not clear what material gain one derives by gratuitous damage to property.

There is evidence that persistent overt and covert antisocial behaviors have distinct developmental pathways (56). Overt aggressors proceed from minor aggression to fighting to major acts of violence. The covert pathway leads from shoplifting and lying to property damage to fraud and burglary. The implication is that while only a minority progress to the most severe forms of misconduct, those who do had progressed through the earlier stages of the respective pathway.

In addition to unjustified, injurious behaviors directly applied to a victim or property, another form of interpersonal harm occurs when one seeks to undermine the relationships or social standing of another person. Examples of this so-called indirect, or “relational,” aggression include ostracism and rumor-mongering. This form of antagonistic behavior seems to be most prevalent among girls and young women. Study of this topic has proliferated in social developmental psychology (57) involving mainly community samples, and to a far lesser degree in psychiatry. One obvious reason is that these behaviors are in themselves unlikely to be the chief complaint that leads to clinical referral or criminal justice involvement. The more common scenario in clinical settings is that child patients are the victims of these peer-inflicted adversities. Their attempts at retaliation in kind are prone to backfire, since their lack of social savoir-faire and popularity often leads to poor selections of rumor topics, rebuttals, or audiences. It is therefore unclear how much harm relational aggressors seen in clinical settings actually cause, since effective attacks of this kind seem to require “social capital”— status, credibility, and influence in a peer network (58)— that children seen for mental health care seldom enjoy. Nonetheless, youth whose peers report they display relational and physically aggressive behavior receive teacher ratings of behavioral problems that are somewhat higher than physical-only aggressors (59). Even if relational aggression is not currently on the radar as a strong clinical concern by itself, it seems useful to consider such behavior at least for its usefulness as a marker of impaired peer relationships among youth seen in psychiatric care.

A contemporary wrinkle on this issue is the potential for youth to use the Internet to defame peers with anonymity or even impersonating another individual. Schools take this type of misbehavior very seriously, especially when they include threats, even very oblique ones (e.g., “Better watch out”). School suspensions and requests for mental health consultation have grown for such conduct.

Evidence from several sources implicates affect disturbances in aggression. The correlation between negative affective features (irritability, lability, anger, dysphoria, frustrability) and disruptive behavior is well established (54,80). The correlation between emotional instability and aggression in particular is extremely high among youth (81). Studies of comorbidity substantiate the cooccurrence of disruptive disorders and mood and anxiety disorders (61,63,64,82,83).

One shortcoming of cross-sectional studies of affective features and aggression is lingering uncertainty about which gives rise to which. However, longitudinal studies of temperament
show that persistent negative affect early in life, seen as unconsolability, low adaptability, and irritability, predicts subsequent aggression (84,85). Parental reactions to these difficult characteristics may moderate the ultimate impact of difficult temperament (86,87). From a diagnostic standpoint, longitudinal studies also indicate that early ODD confers heightened risk for adolescent mood disorder (88). This is not a surprising finding because, despite its frequent alignment with conduct disorder, half the symptoms of ODD describe hostility arising from negative affect.

Among youth with conduct problems, those with negative affect symptoms tend to be more aggressive and to experience worse functional outcomes. Unfavorable outcomes include more hospitalizations, police contacts, impaired social relations, substance abuse, and less improvement with treatment (89,90,91,92,93).

As noted earlier, serotonergic functioning in depressed patients and many aggressive individuals without a primary mood disorder shows similar deviations from controls (94). Findings among children have been less consistent, though, and seem moderated by age, family history, degree of irritability, abuse history, and perhaps ethnicity (30,95,96). One recent report indicated that among children with disruptive behavioral problems, those who had normal prolactin elevation to d,l-fenfluramine had fewer conduct problems in adolescence than children who showed the blunted response more typical of depressed patients (50).

Affective disturbances may influence aggression through both abnormalities of sustained mood and more momentary emotional dysregulation. Rageful episodes are common among adults with major mood disorders (97,98). Similarly, irascibility and explosiveness develop often in the context of posttraumatic stress disorder (PTSD). Aggressive behavior therefore can arise as a complication of mood and anxiety disorders.

In addition, emotion regulation can be disturbed episodically, with or without persistent problems in prevailing mood, hedonic tone, or anxiety (99,100). Aspects of emotion regulation that are relevant to aggression include high emotional reactivity, poor emotion modulation, lability, and slow recovery from upset (101,102,103). Vulnerability to hot temper has been also associated with possible defects in social information processing, whereby children too readily impute bad intentions to others who may have unintentionally caused some annoyance for them (104). However, depressed children show a similar phenomenon (105), raising the possibility that negative affect distorts appraisals of threat.

Among aggressive children, these features often do not always summate to clear mood disorder diagnoses based on traditional criteria. The result is that similar phenomenology attracts a variety of diagnostic designations. So, prominent lability and irritability that comes and goes may signify a form of mania to some clinicians, while to others the same features manifest emotional impulsivity thought to accompany ADHD. Intermittent explosive disorder strikes others as an appropriate characterization, though outbursts are usually more than intermittent, and interepisode functioning more impaired, than IED usually connotes. Vulnerability to easy emotional upset leads yet others to emphasize inflexibility that can be characteristic of pervasive developmental disorders. And in many settings, the high defensive reactivity that accompanies affective/impulsive aggression suggests sequelae of trauma. All of these can be very accurate and clinically useful characterizations that explain the context in which aggressive behavior emerges, but it is not certain to what extent clinician predilections, in contrast to patient history, inform such decisions. The coming years should bring greater clarity to this topic, accompanied, hopefully, by advances in our basic understanding of how emotion arises, changes, and become perturbed to produce psychiatric illness.

With the possible exception of posttraumatic stress disorder, discussed later, anxiety disorders by themselves seldom increase the liability for aggressive behavior. The situation changes, though, when comorbid conditions enter the picture. Anxious children with ADHD and ODD are more likely to become behaviorally unmanageable, perhaps by virtue of impulse control problems, making it more difficult for them to tolerate anxious discomfort. For instance, efforts to interrupt compulsive rituals for a child with obsessive-compulsive disorder or to enforce school attendance with a child who has separation anxiety can at times provoke aggressive dyscontrol. A frequent comorbidity with anxiety and with ADHD is chronic tic disorders, including Tourette syndrome, a particularly difficult combination that has a high prevalence of rage attacks and destructive behavior (106).

Besides these “hot” affective features, callousness and under emotionality may, as mentioned earlier, influence aggressive behavior used for instrumental goals (38,107). These individuals appear to display rather blunted emotional reactivity to the distress of others, a stimulus that is thought to inhibit gratuitous violence in most people (44). Similarly, the disapproval of others appears to carry little significance for them and it seems they are more interested in asserting control and gaining advantage over others than in companionship. Perhaps as a partial result of this indifference, the antisocial behavior of psychopathic individuals is especially refractory to current treatments.