The Diagnostic and Statistical Manual of Mental Disorders Fifth Edition, known as the DSM-5, states five criteria required to diagnose split personality disorder, according to WebMD. The condition is also known as dissociative identity disorder.
The criteria for diagnosing dissociative identity disorder includes two or more distinct personalities being present, the occurrence of amnesia, and that the person being diagnosed has trouble functioning in everyday life as a result of the condition, notes WebMD. Additionally, the condition must not be a part of cultural or religious rituals, or be caused by drugs such as alcohol or medication. The accurate diagnosis of dissociative identity disorder often takes time, because it shares some of its symptoms with other psychological disorders.