This chapter delineates the developmental trauma disorder (DTD) diagnosis proposed by the National Child Traumatic Stress DSM-V Taskforce. The numerous clinical expressions of the damage resulting from childhood interpersonal trauma are currently relegated to a whole variety of seemingly unrelated comorbidities, such as conduct disorder, attention-deficit hyperactivity disorder (ADHD) and separation anxiety. The chapter discusses the effects of childhood interpersonal trauma on brain activity, self-awareness and social functioning. Several large-sample studies have examined the causal relationship between childhood interpersonal trauma and DTD symptoms. These studies have documented the correlations of age of first trauma exposure, trauma severity and duration of exposure with DTD symptoms. Contemporary neuroscience research suggests that effective treatment needs to involve learning to modulate arousal, learning to tolerate feelings and sensations by increasing the capacity for interoception and learning that, after confrontation with physical helplessness, it is essential to engage in taking effective action.