Other diagnosis are often wrongly ascribed to the client (i.e. Borderline Personality Disorder or a psychotic disorder). A careful assessment needs to be done to rule out all other possible diagnosis. The assessment process may include neurological testing and a complete medical exam. Also, Administering assessment tools such as the MMPI, the Dissociative Experiences Scale (DES), the Structured Clinical Interview for Dissociative Disorders (SCID-D) and the Dissociative Disorders Interview Schedule (DDIS) should be considered by clinicians treating possible DID clients.
A careful assessment would cover the basic issues of Marla's history, inquiring about her sense of self, other symptoms such as depression, anxiety, rage, flashbacks, intrusive memories, inner voices, amnesia, nightmares or recurrent dreams. It would also include issues around safety, hers and those around her, any relationship problems, substance abuse, eating disorder behaviors, and her current support network.