Autoimmune encephalitis is a rapidly evolving topic in both neurology and psychiatry. A recent international consensus paper defined criteria for possible, probable and definite autoimmune psychosis (AP) inspired by the principles established in neurology for the definition of autoimmune encephalitis (AE). This has stimulated much clinical research on AP, but also criticism of the validity of the criteria for possible AP, justifying further clinical investigation such as lumbar puncture. In clinical practice, it is often difficult to decide how far diagnostic procedures such as lumbar punctures and immunotherapies should go in unclear cases. Against this background, this review has three aims: First, we summarize and compare the available concepts for the diagnosis of AP in a systematic literature review. Second, we present an overview of typical specific and non-specific findings that can be obtained in laboratory, electroencephalography, magnetic resonance imaging, cerebrospinal fluid, and [