The is a diagnostic tool. It has evolved over the decades, as have the classifications and criteria within its pages. It is used not just for diagnosis, however, but also for billing, access to services, and legal cases. Not all practitioners are in agreement with the content and structure of the , and dissociative disorders are one such area. These disorders can be difficult to distinguish and diagnose. There is also controversy in the field over the legitimacy of certain dissociative disorders, such as dissociative identity disorder, which was formerly called multiple personality disorder.