**5. Neuro-developmental perspective of PTSD**

Human development starts from conception and continues until the end of life. Along this developmental pathway, earlier years witness the highest speed and the most complex changes. Moreover, recent neurological research studies have concluded that the human brain is the fastest developing organ in the first years of life. Not only physically that the child's brain reaches its almost full size by age four, but also by making almost 700 million snaps connections every second completing at least 80% of its functioning capacity. This makes neurological development the most decisive developmental process in the early years [64]. It also points to the fact that ACE become the major cause of long-term emotional problems, including PTSD.

Worldwide, children are often exposed to serious traumatic events, such as war, displacement, famine, and violence, that all disrupt a child's secure family structure and lead to long-term stress. Mental health problems affect around 10–20% of the child population worldwide [65]. Trauma is common in children and adolescents

and may lead to PTSD. PTSD refers to maladaptive responses to at least one severe, threatening event (serious injury, threatened death, or sexual violence) by DSM-5, and the stress response, emotion regulation problems, and threat learning are indicated as common diagnostic symptoms of PTSD are; intrusion, avoidance, negative alterations in cognition and mood and arousal [66]. These cognitive symptoms have led researchers to examine the neurodevelopmental dimension of PTSD in the light of neuroscience studies.

According to the recent neurodevelopmental research results psychological as well as physiological responses to traumatic events such as being unable to bond with primary caregiver might lead to trauma having a long-term neurological impact on a child's psycho-social development and neurological functions [67, 68]. Such psychological problems, referred to as PTSD, are often associated with multiple psychosocial problems ranging from delinquency, poor academic performance to, alcohol and substance abuse, and even to suicidal attempts. Moreover, children exposed to traumatic events will have emotional, social, and physical developmental problems later in life [69]. It was observed that children exposed to traumatic events performed lower performance on cognitive and intellectual abilities than the children without a diagnosis of PTSD [70]. Besides, according to research results verbal and nonverbal intellectual capacity, mean IQ scores, language delay, sensory processing, memory, aggressive behavior, visual processing, affect, and behavior problems can be seen in children [71].

Neuroimaging research with PTSD indicates both functional and structural abnormalities in the front limbic area responsible for emotion regulation and threat processing. Such as decreased gray matter volume in ventromedial prefrontal and dorsal anterior cingulate cortex seen in structural analyses and hyperactivation of the insula, amygdala, and mid anterior cingulate cortex, smaller frontal-occipital circumference seen in functional analyses [72, 73]. Both structural and functional differences are also observed in the prefrontal cortex and limbic system (hippocampus and amygdala). Therefore, memory, emotion and excite function problems may accord exposure to stress [74].
