It seems that in addition to media violence changing brain function, researchers have identifed that children's exposure to family violence changes a child's threat perceptions, sometimes for life. 
Estimates of physical abuse to children range from 4 to 16%, while exposure to witnessing violence between parents affects between 8 and 25% of kids . That is a lot of adults fighting. It's also a high number of children being shown that the way to resolve communication difficulties is to yell, shout, and lash out physically.
When kids see their parents fighting they [the children] are more prone to developing a mental illness, including anxiety . It is also linked with the child being unconsciously hypervigilant to anger  for the rest of their life.
The authors suggest that a child's development is hindered in 3 ways when they are physically abused, or when they see parents engage in physical violence:
- Children may have poor relational skills, which may affect their thinking skills and attention;
- The child has increased vulnerability to stressors and anxiety throughout their life;
- It may predispose the child to react aggressively to others.
The researchers showed 43 children pictures of faces, some of which displayed angry expressions. FMRI equipment measured changes in blood flow throughout the children's brain while they saw the images. When blood moves to a specific region of the brain, the scientists infer that the region has been activiated by sight and perception of the image.
Of the 43 study participants, 20 of the children had been exposed to physical abuse or seen their parents engage in violence towards each other. These 20 children had significantly more activity in amygdala and anterior insula regions of their brains when they saw images of angry faces. These are the same regions that detect threats and anticipate pain, and are highly active in soldiers who have been exposed to combat, and in adults with anxiety disorders.
When we have been exposed to family violence, it's essential to get psychological support to deal with it. There are sliding-scale counseling services in many towns and cities to suit people of diffierent incomes.
The feelings we felt at the times we were exposed to the violence lie buried alive in our unconscous unless we have been able to fully feel the feelings without fear of being hit, told to shut-up, or be punished. Feelings that are unexpressed lead to hypervigilence to anger and other threats, which makes our relationships extremely stressful, and may cause anxiety in later life.
It's never too late for parents to change and start modeling different behaviors to their children. Repairs can be made to the parent-child relationship with the right support.
 McCrory, E. J., De Brito, S. A., Sebastian, C. L., Mechelli, A., Bird, G., Kelly, P. A., & Viding, E. (2011). Heightened neural reactivity to threat in child victims of family violence. Current Biology, Published online Dec 6th, 2011.
 Gilbert, R., Widom, C. S., Browne, K., Fergusson, D., Webb, E., and Janson, S. (2009). Burden and consequences of child maltreatment in high-income countries. The Lancet, 373, 68–81.
 Scott, K. M., Smith, D. R., and Ellis, P. M. (2010). Prospectively ascertained child maltreatment and its association with DSM-IV mental disorders in young adults. Archives of General Psychiatry, 67, 712–719.
 Pollak, S. D. (2008). Mechanisms linking early experience and the emergence of emotions: Illustrations from the study of maltreated children. Current Directions in Psychological Science, 17, 370–375.