Autoimmune encephalitis is widely known from books and movies such as "The 8-Year Engagement"and "Brain on Fire". Anti-NMDA receptor encephalitis is common in relatively young females and the most frequent cause of neuronal autoantibodies. VGKC complex antibody encephalitis, which has the second highest frequency, is common in relatively elderly males. In addition to these, neurotransmitter receptor antibodies involved in the pathology of psychiatric disorders have recently been discovered one after another and become detectable. Furthermore, although studies of patients diagnosed with endogenous psychosis were often criticized because they investigated serum samples, the existence of neuronal autoantibodies in the cerebrospinal fluid has recently been reported frequently. The expectations regarding immunotherapy as new and effective treatment for psychotic disorders are increasing. The group of patients who present with only psychiatric symptoms (no or only subtle neurological symptoms) due to neuronal membrane or nuclear autoantibodies is referred to as having`Autoimmune Psychosis'. Autoimmune psychosis can be distinguished from typical autoimmune encephalitis.
 However, the concepts of "autoimmune encephalitis" in the field of neurology and "autoimmune psychosis" in the field of psychiatry differ markedly, and the current situation is confusing as there are various diagnostic criteria as well as differences in samples (serum, spinal fluid) and antibody testing methods, and there is still no test and treatment method that is covered by insurance for "autoimmune encephalitis".
 Early detection and treatment of anti-NMDA receptor encephalitis are effective, and any delay in treatment is associated with a poor prognosis. Therefore, it is important to consider autoimmune psychosis as a differential diagnosis for various psychiatric disorders, such as schizophrenia, mood disorders, epilepsy, and sleep disorders. While it is important to detect neuronal autoantibodies and make a definitive diagnosis for the basis of immunotherapy, it is also necessary in practice to consider active immunotherapy even in patients with a probable diagnosis.
 Authors' abstract