A new autoimmune encephalitis, Anti-N-methyl-D-aspartate (NMDA) receptor encephalitis, with a characteristic clinical course was proposed in 2007 by Dalmau et al. A stereotypical clinical course during phases includes a non-specific flu-like prodrome (subfebrile temperature, headache, fatigue) which is followed by a psychotic stage with bizarre behavior, disorientation, confusion, paranoid thoughts, visual or auditory hallucinations and memory deficits. Acute onsets of atypical psychosis are usually considered initially, and the patients are often admitted to psychiatric centers. Organic brain disease is considered only after the patients develop seizures, autonomic instability, dyskinesia, or decreased level of consciousness, but in some cases, psychiatric symptoms are foremost throughout the disease course, lacking the symptoms associated with encephalitis. These cases are often diagnosed as acute schizophrenia. Approximately half of affected patients are found to have an ovarian teratoma, with early tumoral excision reported to be associated with an improved recovery phase. A series of studies report about 10% positivity of anti-NMDAR antibody among schizophrenia patients, suggesting autoimmune encephalitis contributes to many currently diagnosed cases of acute schizophrenia, but the specificity and functional roles of the findings of antibody positivity are still obscure. Nevertheless, the existence of the unquestionable cases suggest an association between the causative roles of the autoimmune encephalitis and some forms of acute psychosis. I have been doing sleep research for 32 years, focusing on narcolepsy, a prototypical hypersomnia with REM sleep abnormalities, due to the loss of orexin/hypocretin neurons. It was revealed that autoimmune mechanisms are involved in sporadic and symptomatic cases of narcolepsy.
 In this review, I will introduce the history and update new findings of narcolepsy and those of autoimmune encephalitis/encephalopathy in the Sleep and Psychiatry research fields.
 <Author's abstract>