As expected, there was also limited concordance between schizophrenia and ADHD (r = 0.0705), particularly for downregulated genes (Fig. 4b), and six (MAD1L1, KDM4A, IPO13, ATP6V0B, DPH2, PTPRF) of the nine placental genes associated with ADHD were also significantly associated with schizophrenia (Supplementary Data 45, 54). Here, KDM4A is linked to attention deficit-hyperactivity disorder.