Prior studies have shown that the OXTR rs53576 A allele-specific genotype is associated with susceptibility to a disturbed mental state; thus, we hypothesized that the association, if any, between maternal postpartum depression and child behavioural problems, as represented by internalising problems and/or externalising problems, would be found in the A allele, but not the G allele, of OXTR rs53576. This evidence concerns the gene OXTR and postpartum depression.