The gene for a biosynthetic enzyme of polySia, ST8SIA2, actually contains mutations or significant SNPs that are statistically associated with mental disorders, e.g., SNP-7, rs3759916, and rs3759914 from schizophrenia patients in a Japanese population [35] and rs2168351 from bipolar disorder patients [45]. This evidence concerns the gene ST8SIA2 and schizophrenia.