It is relatively well-known that patients with encephalitis present with psychotic symptoms in the early stages of the disease. In particular, anti-N-methyl-D-aspartate (NMDA) -type glutamate receptor antibody encephalitis (NMDAR encephalitis), described by Dalmau in 2007, has become well-known in psychiatric practice to identify autoimmune encephalitis because it often presents with psychiatric symptoms. On the other hand, knowledge of the relationship between abnormalities of the immune system and psychiatric disorders is accumulating, and some psychiatric patients are beginning to be considered to have immunological mechanisms associated with their pathophysiology.
 In the 2020 Psychoimmunology Expert Meeting, involving a subcommittee of the World Psychiatric Association, diagnostic criteria were proposed for "autoimmune psychosis". By evaluating the diagnostic criteria for autoimmune psychosis and red flags of autoimmune encephalitis, it is hoped that efforts will be made to re-evaluate primary psychiatric disorders from an immunological perspective and establish appropriate treatment.
 In this paper, we first outline the relationship between the immune and nervous systems, the relationship between immune abnormalities and psychiatric disorders, the pathogenesis of autoimmune encephalitis, and diagnostic criteria for autoimmune psychosis. Next, we will present actual cases we have encountered and discuss key points regarding clinical diagnosis, treatment, and follow-up. We also report on our work involving psychiatric patients with autoimmune thyroid disease and systemic lupus erythematosus, two of the most common autoimmune diseases.
 A better understanding of the immune and nervous systems, including autoantibodies, may lead to a better understanding of the biology of psychiatric disorders and their treatment. Continued accumulation of cases and elucidation of the pathophysiology are needed in the future.
 Authors' abstract