PDE4B and schizophrenia: Five of these top eight LD-independent loci (MTHFR, PDE4B, DAOA, ARVCF, TRAM1L1/NDST3) were not located within risk loci identified in the largest schizophrenia GWA study produced by the PGC and three loci (MTHFR, DAOA, ARVCF) had never been implicated by a schizophrenia GWA study.