When a person has been exposed to certain kinds of stressful situations, such as ongoing family violence, the amygdala may become overreactive. When this occurs, the body's alarm systems react more quickly and more energetically to threats than they do in normally reactive people. This neural phenomenon has been documented in soldiers who show symptoms of post-traumatic stress disorder or PTSD.

But it is not just the brains of those exhibiting the symptoms of PTSD that are affected. Neurologic examinations have shown that even soldiers returning from combat zones who appear emotionally normal have amygdalas that are unusually reactive -- ready for trouble and ready to react -- if they are threatened.

A recent study published in Current Biology showed that children who were exposed to family violence showed changes in the reactivity of their amygdalas and AIs that were similar to those seen in soldiers returning from combat. Even when these children showed no outward signs of unusual levels of depression or anxiety, studies of their brain activity showed that their systems were in a vigilant gear and overly reactive to perceived threats.

Twenty children who had been exposed to family violence and 20 control-matched peers were shown pictures of angry, sad, or neutral faces. The children all had normal outward levels of anxiety and depression. Their neurological response to the pictures were measured by functional magnetic resonance imaging (fMRI). When viewing the angry faces, the children who had been exposed to family violence showed a greater level of activation of the amygdala and AI regions compared to controls. They did not overreact to the sad or neutral faces. The degrees of activation mirrored the severity of the violence exposure they had experienced; the more violence in their lives, the stronger the neurological response in the brain's stress regions.

The researchers concluded that children who have been exposed to family violence, even if they are not showing overt symptoms, have a heightened neural responsiveness to stress. The authors point out that this may be a beneficial adaptation on the short term to a threatening environment but it may pose problems in the long term.

The researchers suggest this excessive neural responsiveness to stress may negatively impact a child's development in several ways. When a child is devoting the majority of his or her cognitive and emotional energy dealing with real or perceived threats, he or she has less time and mental energy to take on age-appropriate challenges and to develop age-appropriate social and thinking skills.

Simply put, it's much harder to play imaginatively when you are worried all the time.

When the neurologic pathways involved in the stress response are overactive from daily life stressors this chronic stimulation renders the stress response more volatile and perhaps more extreme than is appropriate to the level of threat. These children may rapidly escalate their physical and emotional response in a way that is not in proportion to the situation. And finally, children who perceive a threat and have over activated stress responses may react by being aggressive toward others to protect themselves. This reactive aggression is a maladaptive response that may cause behavioral difficulties in social, academic, and home settings.