Pathology and evaluation of childhood aggression

April 1, 2012

Aggressive behavior could be considered developmentally normal in most children, but when aggression becomes more intense and occurs frequently, intervention may be necessary.

Key Points

Pediatricians play an important role in the mental health of their patients as part of leading the medical home.1

Up to 10% of all children and adolescents have mental health disorders, yet only about 20% of children receive proper care.2 Clinical access to mental health specialists is limited, so it's important that primary care providers be able to evaluate and manage mental health problems.

Children with psychosocial difficulties may use medical resources at a higher rate, so providing longitudinal, comprehensive care with an emphasis on prevention and promotion of healthy lifestyles within the medical home can have economic advantages.

What is aggression?

Aggression is defined in Webster's New World College Dictionary as forceful or attacking behavior, either constructively self-assertive and self-protective or destructively hostile to others or to oneself. Aggression can be a positive behavior if one is protecting a loved one from danger, and it is a plus in many sports. Destructive aggressive acts, whether verbal or physical, are intended to harm a living being, which includes property destruction and self-injurious behavior.

From a developmental and evolutionary perspective, aggression is considered normal behavior and critical to survival in primitive cultures. Prospective studies of young children show that the peak frequency of aggression in humans occurs between 2 and 4 years.3 In many cases, aggressive behavior in young children would be considered developmentally normal (eg, temper tantrums). Aggression may be considered abnormal when it is chronic in nature or occurs in greater frequency or greater intensity than expected. About 10% of elementary school children have chronic physical aggression, but by adolescence the incidence falls to 5%.

Types of aggression

The different aspects of aggression are important to understand. Types of aggression include impulsive (reactive), proactive, and maladaptive.4

Reactive aggression is best understood as an angry, defensive response to a threat or provocation. This sort of aggression may be seen as "hot"-emotional and impulsive and generally not goal oriented.

Proactive aggression is seen as premeditated and calculated, with an end goal in mind. Thus, definitions of aggression differ according to their antecedents and purposes.

Maladaptive aggression is defined as behavior, because of its intensity, frequency, and duration, that is not adaptive to the individual and is out of proportion to its precipitants and social contexts.5


The pathophysiology of aggression involves the amygdala and limbic system and its connections.

A hypothetical balance of systems exists that regulates emotional reactions to stimuli.6,7 The bottom-up system involves the amygdala, which embeds emotional significance in stimuli. It appears to dominate emotional processing in childhood and adolescence and is driven by pubertal hormones. "Hot cognitions," such as those seen in stressful and arousing situations, tend to increase amygdala activity.

The top-down system involves the prefrontal cortex, which integrates emotional and cognitive information and regulates emotional reactivity. It is a later-maturing system and represents measures of executive function such as planning and considering consequences ("cold cognitions").

The amygdala is closely tied to aggression through its input from cortical regions and projections to the hypothalamus and brainstem areas involved in attention, arousal, and autonomic function.8 Reactive aggression is associated with an overactive amygdala and limbic system.9 Disturbed amygdala function also is found in proactive aggression, most often seen in conduct disorder (CD) and criminal behavior. In general, reduced amygdala activity is associated with more aggressive symptoms and callous-unemotional traits.10,11

Systems such as the sympathetic and parasympathetic nervous systems help regulate physiologic arousal, with involvement from the hypothalamic-pituitary-adrenal axis (HPA). These systems may be dysregulated in children with chronic aggression and reflect genetic-environmental factors.3 It's been suggested that poor parenting and early environmental stresses may lead to methylation of the glucocorticoid-receptor gene, with subsequent down regulation of the HPA axis and increased aggression.7 Oppositional defiant disorder (ODD) and CD are associated with lower baseline levels of arousal that may reflect a poorly regulated HPA axis.

Other developmental processes such as myelination and synaptic pruning are influenced by life experiences and speak to the important role the environment plays in the integrity of systems felt to regulate adaptive responses to social input.12

Pediatricians can use awareness of these developing systems to educate families and support informed treatments.