Consciousness is something that every child understands, yet scientists and philosophers struggle to explain it. Consciousness provides an essential human quality to life experience, as one depends on it to organize and prioritize their memories, emotions, and actions. Unraveling the enigma of consciousness, and its impairment, has been a thorny road to travel, often littered with confusion and denial. This has been particularly true regarding understanding of the effects of psychological neglect and trauma on ones biopsychosocial systems. Consciousness is alterable by several influences: alcohol, drugs, anesthesia, childhood neglect and abuse, traumatic experiences, neural injury, and disease. This chapter begins by briefly exploring global alterations of consciousness, such as anesthesia, coma, and vegetative states. This allows us to examine the impact of these pervasive states of impaired consciousness on the neural systems, noted earlier. It then examines in detail disorders of consciousness induced by psychic neglect and trauma.