PhD defence Y.R. (Youri) Berends-Albeda

Dissertation in short:

Converging evidence reveals that neuropeptides such as oxytocin and vasopressin are associated with a wide variety of affiliative behaviors. Oxytocin was originally known for its effects on uterine contractions during labor and for its enhancing effect on lactation, but has proven also to be crucial in the attachment between mother and infant after birth and regulating trust in others. Vasopressin is known for its effect on the regulation of the blood pressure. Behaviorally, vasopressin seems to have an opposite effect as it seems to enhance both defensive and offensive aggressive behavior. However, the effects of oxytocin and vasopressin in human populations have been difficult to replicate and their effects on behavior tend to depend on a multitude of internal and environmental factors. This thesis focused on the specific role of oxytocin and vasopressin in relation to trust and aggression by combining observational, experimental, cross-sectional and idiographic study approaches in healthy subjects and male forensic psychiatric patients with personality disorders. This study shows that oxytocin can enhance pro-social behavior, but only in an according environment. If the context is perceived as ambiguous or hostile, oxytocin enhances a defensive and protective attitude. This thesis contributes to the formulation of a more nuanced vision on oxytocin and vasopressin, which does, however not respond to the hope of many forensic therapists that oxytocin might enhance pro-social behaviors. The large interpersonal variation in hormonal levels and the large differences between different patient groups limit the individual-level clinical implementation of findings regarding oxytocin and vasopressin.