Spaw rightly talks about the damage to the brain and mind done by parents' drink or drugs. So far nobody has mentioned another source of trouble - brain damage caused by blows to the head or by shaking.

A brain-damaged person is usually an angry person.

A newspaper article today (or yesterday) said that the boy in Ohio had often been sent to school unwashed and in dirty clothes. What do you want to bet that the adults who failed to keep him clean also failed to protect him from blows to the head?