Of relevance to the idea that a precipitous drop in maternal circulating steroid hormones (notably oestrogens) may somehow elicit psychosis in the postpartum period, work in rats has demonstrated that ovariectomy, and the associated decrease in circulating oestrogens, results in significantly decreased Ccn3 (Nov) expression in the hippocampus (48). This evidence concerns the gene CCN3 and psychotic disorder.