http://www.huffingtonpost.com/dr-dou..._b_765908.html

Dr. Douglas Fields

"...Studies have shown that children exposed to serious psychological trauma during childhood are at risk of suffering increased psychiatric disorders, including depression, anger, hostility, drug abuse, suicidal ideation, loneliness and even psychosis as adults. Using modern brain imaging, the physical damage to these children's brain development can be seen as clearly as a bone fracture on an X-ray. Early-childhood sexual abuse, physical abuse and witnessing domestic violence undermine the normal wiring of brain circuits, especially those circuits connecting the left and right sides of the brain through a massive bundle of connections called the corpus callosum. Impairment in integrating information between right and left hemispheres is associated with increased risk of craving, drug abuse and dependence, and a weakened ability to make moral judgments....

A series of studies... shows that even hostile words in the form of verbal abuse can cause these brain changes and enduring psychiatric risks for young adults... in 2006, the researchers showed that parental verbal abuse was more strongly associated with these detrimental effects on brain development than was parental physical abuse. In a new study... they report that exposure to verbal abuse from peers is associated with elevated psychiatric symptoms and corpus callosum abnormalities. The main causes are stress hormones, changes in inhibitory neurotransmitters, and environmental experience affecting the formation of myelin electrical insulation on nerve fibers. The most sensitive period for verbal abuse from peers in impairing brain development was exposure during the middle school years. Why? Because this is the period of life when these connections are developing in the human brain, and wiring of the human brain is greatly influenced by environmental experience...

... Our brains are the product of the environment in which we are nurtured through the first two decades of life... Our experience during childhood and adolescence determines the wiring of our brain so powerfully that even processing of sensory information is determined by our childhood environment. Whether or not we can hear eight notes in a musical scale or 12, or whether we find symmetry in art beautiful or boring, or whether we can hear the difference in sound of the English letter "R" vs. "L", depends entirely upon whether our brains wired up during childhood in Western culture or Asian culture. The neural circuitry underlying those sensory perceptions is directed by what we experienced in early life, and these circuits cannot be rewired easily in the adult brain..."