Dissociative Identity Disorder
You are probably looking at the title and thinking "hmm, I've never heard of that", yet in truth you have. It was once reffered to as multiple personalities, up until the early 90s. This disorder, DID for short, is a disorder caused by early childhood trauma, ranging from physical abuse, mental abuse, sexual abuse, and the list goes on. This disorder allows the child to become detached from any trauma that is occurring. DID in short is when someone has multiple people in one body, all distinct in their own way. Do remember, most who have a history of abuse may not have this disorder or even know they have it. There are fewer than 200,000 cases in the US per year alone, not including those who aren't fully diagnosed.