This study tested 619 patients in Germany for antibodies and RNA of the Borna Disease Virus (BDV) to examine the link between mental disorders and BDV infection. 416 psychiatric patients and 203 healthy controls were tested using reverse transcription polymerase chain reaction (RT-PCR) and serum testing. The results found that 40 of the psychiatric patients tested seropositive for BDV antibodies compared to only 3 of the controls. Of those psychiatric patients, 11 had schizophrenia and 7 of those 11 schizophrenic patients tested positive for BDV RNA strands. This provides evidence of a link between BDV infection and schizophrenia, as most BDV cases appeared in patients with schizophrenia.