Complexly traumatized youth frequently suffer from body dysregulation, meaning they over-respond or underrespond to sensory stimuli. For example, they may be hypersensitive to sounds, smells, touch or light, or they may suffer from anesthesia and analgesia, in which they are unaware of pain, touch, or internal physical sensations. As a result they may injure themselves without feeling pain, suffer from physical problems without being aware of them, or, the converse – they may complain of chronic pain in various body areas for which no physical cause can be found.
Effects of Complex Trauma. (2014). Retrieved September 7, 2014.

Think of what it is like for young children to be in traumatic situations. They can feel totally helpless and passive. They can cry for help or desperately wish for someone to intervene. They can feel deeply threatened by separation from parents or caretakers. Young children rely on a "protective shield" provided by adults and older siblings to judge the seriousness of danger and to ensure their safety and welfare. They often don't recognize a traumatic danger until it happens, for example, in a near drowning, attack by a dog, or accidental scalding. They can be the target of physical and sexual abuse by the very people they rely on for their own protection and safety. Young children can witness violence within the family or be left helpless after a parent or caretaker is injured, as might occur in a serious automobile accident. They have the most difficulty with their intense physical and emotional reactions. They become really upset when they hear cries of distress from a parent or caretaker.
Understanding Child Traumatic Stress. (2014). Retrieved September 7, 2014. http://www.nctsn.org/resources/audiences/parents-caregivers/understanding-child-traumatic-stress Each year in the United States approximately five million children