Vasopressin plays an important role in the stress response and has been identified as an integral part of the hypothalamic–pituitary–adrenal (HPA) axis as a potential factor in stress-related disorders such as anxiety and depression, but the reason why the AVP system is involved in the regulation of the stress response in PPD is yet to be known16,17. This evidence concerns the gene AVP and progressive pseudorheumatoid arthropathy of childhood.