DissociativeIdentityDisorder (DID), formerly known as MultiplePersonalityDisorder (MPD), is also referred to as dissociative personality disorder in some publications. It is a type of mental illness that is classified in the Diagnostic and Statistical Manual of Mental Disorders (DSM) as an Axis I dissociative disorder. The following disorders are all causes of dissociative identity disorder: 1. Personality disorder Personality disorder, also known as pathological personality or abnormal personality, refers to the aberrant development of personality that forms a characteristic, distinct, deviation from the social and cultural context in which it is found, and the cognitive behavior patterns recognized by most people. The deviation of personality traits is maladaptive to the environment and significantly interferes with the person’s social and occupational functioning, resulting in the person’s inability to maintain harmonious interpersonal relationships and difficulty adapting to social life. Not only does it cause harm to others, but the person himself or herself also suffers from it or causes suffering. Pathological personality was originally a broad concept, referring to all types of personality abnormalities, and later some scholars found that the original definition of pathological personality, in line with the current term anti-social personality, and thus the emergence of a narrow concept of pathological personality, referring exclusively to anti-social personality, proposed to personality disorders (personality disorders) instead of the broad sense of pathological personality. 2, schizophrenia Schizophrenia is the most common type of psychosis characterized by basic personality changes, splitting of thinking, emotions and behavior, and incoordination of mental activities with the environment. Schizophrenia is the most common group of psychiatric disorders, survey data from six districts in the United States show that its annual incidence is 0.43 permil; ~ 0.69 permil;, 0.30 permil; ~ 1.20 permil; over 15 years of age (Babigian, 1975), and 0.09 permil; in some parts of China, according to International Pilot Survey of Schizophrenia (IPSS) data, 20 centers in 18 countries, over 20 years of investigation of more than 3,000 people reported that the annual incidence of schizophrenia in the general population ranged from 0.2 permil; to 0.6 permil; with an average of 0.3 permil; (Shinfuku, 1992). 3, dysthymia Dissociative (conversion) disorders [dissociative (conversion ) disorders] are a group of psychiatric disorders that are dominated by dissociative and conversion symptoms caused by significant psychiatric factors such as major life events, internal conflict, emotional arousal, suggestion or self-referral, and acting on the susceptible individual. Dissociative symptoms, also known as dysthymic psychotic symptoms, refer to the partial or complete loss of self-identification and memory of the past, and are manifested by reduced range of consciousness, selective amnesia, or psychotic outbursts. Conversion symptoms, also known as dysthymic somatic symptoms, are when the patient manifests the discomfort that occurs when experiencing unresolved problems and conflicts in the form of a variety of somatic symptoms. Hysteria has been described as a great disease or disease mimic because it can appear to resemble any disease. The main manifestations are a variety of somatic symptoms, narrowed consciousness, suggestibility, selective amnesia or emotional outbursts, and other psychiatric symptoms, but no corresponding organic damage can be identified as the basis of its pathology.