Oxytocin, vasopressin, and their crosstalk in sexually-dimorphic psychiatric conditions.

Autism spectrum disorder (ASD) and anorexia nervosa (AN) are prototypical neuropsychiatric conditions showing striking but opposite sex differences. ASD is about four times more prevalent in males, whereas AN occurs roughly ten times more often in females. Despite these contrasting ratios, both disorders share clinical features such as impairments in social behavior and cognition, atypical eating patterns, early onset, and reduced emotional awareness. Moreover, their comorbidity occurs about ten times more frequently than expected from general population rates, suggesting shared etiological factors that may act in opposite and sex-dependent directions. Among potential mechanisms, the neuropeptides oxytocin and arginine vasopressin are implicated in both social and feeding behaviors and are central to sexual dimorphism. These peptides can also interact with each other's receptors, producing both overlapping and opposing effects. This review synthesizes current evidence on oxytocin and vasopressin in relation to social and feeding functions and their dysregulation in ASD and AN, aiming to explain the reason why these two disorders, despite their opposite sex ratios, frequently co-occur.