Vasopressin also referred as antidiuretic hormone (ADH). It is a neurohypophysical hormone and is found in most mammals. It primarily deals with two functions which includes water retainment in the body and constriction of blood vessels. Vasopressin hormone increases water permeability in the distal convoluted tube and kidney collecting duct. It also plays a role in increasing arterial blood pressure by increasing peripheral vascular resistance. It is formed from a preprohormone and synthesized in hypothalamus. It is also known to play a role in sexual motivation and social behaviours.

The present research by the Finnish researchers who looked at around 7000 siblings and twins who were in a relationship for more than a year. Identical and non-identical twins were analysed showed that behaviour of infidelity can be seen as a genetic trait. Further, the researchers found that variations in the vasopressin gene coding were common in women who were reported to have sex with one or more people in the past year. 

These hormones are associated with infidelity as they are found to affect the social and sexual behaviours in humans. 

Infidelity is complex and includes various other factors. The genetic component of infidelity was explored and suggested. Further studies and analysis can help to support the results of this study until then the findings are considered tentative.