Dissociative Identity Disorder
A disorder characterized by the presence of two or more distinct personality states.
Dissociative identity disorder, previously called multiple personality disorder, is usually a reaction to trauma as a way to help a person avoid bad memories.
Dissociative identity disorder is characterized by the presence of two or more distinct personality identities. Each may have a unique name, personal history, and characteristics.
Treatment is talk therapy.
Cluster Number:
Wiki Number: W068
Diagnosis: Dissociative Indentity Disorder (Split Personality)
US Patients:
World Patients: 1.5-2%
Sex Ratio: M;F6
Age Onset:
Brain Area:
Symptoms: at lest two distinct and relatively enduring personality states; involuntary and distressing; 16 identities are typical
Progression: Much of the 18-page Wikipedia description focused on the validity: actual vs. induced by inappropriate therapies.
Causes: May have been 90% from childhood abuse, war or childhood-medical procedures; like PTSD for adults
Medications:
Therapies:
Youtube Video:
Dissociative Identity Disorder in Children and Teenagers
Amazon or Library Book: Dissociative Identity Disorder

I could not find this book on Amazon again,
but your library may still have it or borrow it for you through InterLibrary Loan.