PROBLEM TO BE SOLVED: To provide a technique that allows for objectively diagnosing schizophrenia-related disorders.SOLUTION: A diagnostic marker for schizophrenia-related disorders consisting of an anti-syncytin-1 antibody is provided. Also provided is a diagnostic kit for schizophrenia-related disorders including syncytin-1 protein or fragment thereof. The fragment of the syncytin-1 protein may be a peptide consisting of an amino acid sequence shown in SEQ ID NO 9 or a peptide consisting of an amino acid sequence that is shown in SEQ ID NO 9 with one or more lost, substituted, or added amino acids and is recognizable by the anti-syncytin-1 antibody.SELECTED DRAWING: None
DIAGNOSTIC MARKER FOR SCHIZOPHRENIA AND RELATED DISORDERS, AND USE THEREOF