Patients with antibodies against neuronal surface antigens (NSAbs), including the N-methyl-D-aspartate receptor (NMDAR), typically develop autoimmune encephalitis with characteristic neurological and psychiatric symptoms. 1 In 4% of individuals with NMDAR encephalitis, isolated psychotic episodes occur without simultaneous neurological involvement. 2 This raises the question of whether NSAbs are underdiagnosed in patients with psychotic disorders. Results of studies testing this, however, are contradictory, 3-5 possibly because of differences in the methods of antibody detection. Previously, in a cohort of 475 patients with schizophrenia, we found no one with NMDAR antibodies after excluding 2 false-positive results by combined immunohistochemistry (IHC) tests and cell-based assays (CBAs) across laboratories. 6 In this analysis, we extend these studies to other common NSAbs known to cause encephalitis, aiming to expand the clinical spectrum of psychosis potentially caused by autoantibodies. Methods | The cohort included individuals with psychotic disorders, who were further divided into those with schizophrenia, schizoaffective disorder, brief psychotic disorder, and firstepisode psychosis diagnoses (as defined by the DSM-IV), and