Human beings develop a highly coordinated and flexible system of social behavior and threat evaluation. In this review we focus on the unique role of early life adversity (ELA) in programming deficits in social behavior and threat processing, and provides guidance on future investigations in the areas of stress reactivity and mental health. We propose that neuroendocrine perturbations of hypothalamus-pituitary-adrenal (HPA) axis and gene activity by epigenetic mechanisms may explain how early adverse circumstances may lead to post traumatic stress disorder (PTSD). The detailed exploration of the interaction of stress as environmental factor and epigenetic and genetic regulation in HPA axis may improve targeted interventions among vulnerable individuals. We are convinced that further studies following these directions will contribute to effective prevention and treatment of PTSD in early traumatized patients.