The establishment of ZNF804A as a risk factor for schizophrenia and bipolar disorder is one of several successes arising from recent large-scale genetic studies of major psychiatric disorders. These have implicated common alleles for psychiatric disorders at much higher levels of confidence than previous genetic approaches among which the most robust current findings in schizophrenia are ZNF804A, Neurogranin (NRGN), Trancription Factor 4 (TCF4) and a locus spanning several megabases of chromosome 6 in the region of the Major Histocompatibility Complex (4–7). In bipolar disorder, calcium channel, voltage-dependent, L type, alpha 1C subunit (CACNA1C) and ankyrin 3, node of Ranvier (ANK3) have been strongly supported as susceptibility genes (27). At least two of the specific loci, ZNF804A and CACNA1C, influence risk for both disorders (28) a finding that supports the hypothesis that schizophrenia and BD are not aetiologically distinct. Like ZNF804A, in general, the common risk alleles identified by GWAS have small effect sizes (OR<1.25), although the associated allele at ANK3 may have a somewhat larger, but still weak effect (OR~1.45) (27). It is, however, clear that many more common risk
