Oxytocin and vasopressin in male forensic psychiatric patients with personality disorders and healthy controls

Oxytocin and vasopressin are neuropeptides implicated as modulators of human aggressive behavior. In animal models, administration of oxytocin generally attenuates aggressive behavior, but in humans the effects of oxytocin appear to be more nuanced. Vasopressin seems to have an opposing influence on aggression in animal studies, but much less research has been done in humans. We performed a cross-sectional study in which we measured oxytocin and vasopressin levels in forensic psychiatric male patients with a personality disorder (N = 38) and healthy male controls (N = 108). Elevated salivary oxytocin (B = -0.10, P = 0.02) and reduced urinary vasopressin (B = 0,19, P < 0.01) levels were found in patients compared to controls. Within the patient group urinary oxytocin levels were positively associated with psychopathy scores as measured with the PCL-R (B = 0.02, P = 0.02). These findings suggest that baseline levels in forensic psychiatric patients diagnosed with a primary personality disorder might be counterintuitive, as oxytocin levels are higher than expected and vasopressin levels are lower than those of healthy controls. More generally, the results imply a complex role of these neuropeptides on human behavior, in line with the social salience theory.