Children and adults with DID live with simultaneously active multiple self-states which, unlike the everyday occurrence of multiple self-states that we all experience, are separate from each other. Different fragments of experience are each assigned to a different sense of self with its own way of thinking and behaving and with its own unique memories. DID can be regarded both as an attachment disorder and as a post-traumatic stress occurrence. Much of the way that we think about DID is derived from research into post-traumatic stress disorder (PTSD). Professor Peter Fonagy and others have shown that the most common aetiology for DID is a disorganised attachment followed by abuse at the hands of a caregiver (McQueen et al., Citation2009).