If you think that the children experiencing traumatic events are just those victims of war, incest or rape, orphans and children of divorced parents, think again. Millions of children are exposed to different forms of traumatic events at some point in their lives. These traumatic experiences can be time-limited (such as natural calamities, gang hazing) or chronic and pervasive (such as incest, physical abuse, child neglect and war). [1] One point worth pondering is that most parents are not aware that verbal abuse either directly or indirectly addressed to a child can also be traumatic. In fact, children growing in domestic violence are more vulnerable, making them at high risk for deep emotional, psychological, behavioral, physiological, cognitive and social problems. [1]

Witnessing violence at home, in school, or in the neighborhood poses stress to children of all ages, gender and race. This exposure may yield varying responses among children depending on the type and frequency of the stressor, age of the child, and the level of cognitive and psychological stage of the child. (To better understand the normal psychological state of the child based on age, view Erik Erikson’s classical theory on human development found in this website: http://childstudy.net/erk.php)  Some children may experience shock, fear, unhappiness, numbness, worry, loneliness, and nervousness. Others develop internalizing behaviors such as stomachache and externalizing behavior such as acting out. [2] Furthermore, when the child’s coping mechanisms are not sufficient to deal with the traumatic experience, he may have direct effects of trauma such as acute stress disorder, post traumatic stress disorder (PTSD), conduct disorder, anxiety disorder, phobic disorder, depression, substance misuse, and mood disorder. [3] These range of psychological and psychiatric problems demand a great deal of professional attention and medical treatment. One can not also underestimate the indirect effects of trauma as mediated by its impact on children’s view of the world, maladaptive traits, collapse of social network, dysfunctional relationships as well as family and community breakdown.

Generally, humans, in response to threat, utilize 2 kinds of adaptive response patterns namely: hyperarousal (fight-or-flight) response and dissociative pattern (freeze and surrender) response.  In fight-or-flight response, a child faced with threat has increased released of norepinephrine (a chemical in the brain) which stimulates brain regions responsible for arousal, attention, affect, behavioral irritability, sleep and the startle response. [1] This response becomes sensitized so that any mild stressor which may not have previously produced any response now elicit an exaggerated reactivity. The child is practically in a ‘persisting state of fear’ making them overly sensitive and hyperactive. On the other hand, a child faced with threat may use the freeze or surrender response. There is lack of movement in this type of response which is a form of camouflage in children, decreasing their chance of attracting offenders. However, if the child is sufficiently terrorized, the freezing may advance to complete dissociation. In this case, the child is observed to be going to a different place, becoming numb, robotic, non-reactive, daydreaming, and staring off into space. [1]
If trauma is just one of the experiences a child goes through at some point of his life, how then is it possible for this experience to transform a child’s tranquil world into a horror-filled world that so significantly changes his outlook in life? The answer ultimately lies in the human brain. 

Made up of over 100 billion neurons, the human brain is an amazingly complex organ of the body. Neurons in the brain are highly specialized cells that can change in response to external stimuli. All sensory signals (in this case, sensations associated with the traumatic experience) initiate cellular and molecular changes in neurons, permitting storage of information and ultimately transforming the brain structure and function.[1] Hence, this unique ability of the brain allows the brain to be especially responsive to the environment (external and internal stimuli).

Comparatively speaking, the brains of infants and young children are more vulnerable to variance of experience than the brain of adults. This is because different parts of the human brain develop in sequential order and most mature during childhood, making children most sensitive to environmental input including traumatic experience. [1]. The sad fact about this is that, during infancy and childhood, when humans are most vulnerable to trauma, parents assume that their children are resilient to these unpleasant experiences.

So the next time we parents bump into a heated argument with our spouse, or perhaps decide to physically discipline our children with sticks, belts, etc., think again. You might be just posing threat to the child turning you into a culprit rather than a caregiver and protector.
References:

1) Perry, BD, et.al. Childhood Trauma, the Neurobiology of Adaptation & Use-dependent
    Development of the Brain: How States become Traits. Child Trauma Academy 
    Programs Department of Psychiatry and Behavioral Sciences. http://www.trauma
    pages.com/a/perry96.php

2) Skybo, Theresa (2005). Witnessing Violence: Biopsychosocial Impact on Children.
     http://www.medscape.com/viewarticle/512637

3)  Richard Williams (2006). The Psychosocial Consequences for Children and Young
     People who are Exposed to Terrorism, War, Conflict and Natural Disasters. 
     http://www.medscape.com/viewarticle/533619