The Role of Endogenous Oxytocin in Anxiolysis: Structural and Functional Correlates

Abstract Background Oxytocin is anxiolytic, and administration of synthetic oxytocin in humans reduces amygdala reactivity to negative stimuli. However, it is unknown whether endogenous oxytocin levels—which are heritable and stable across time—attenuate anxiety via similar mechanisms. Methods In this study, we used plasma assays and structural and functional neuroimaging to examine potential anxiolytic effects of endogenous oxytocin in 73 participants. Results We found that higher endogenous oxytocin levels are associated with reduced central amygdala volume and blood oxygen level–dependent activity in response to aversive stimuli. In contrast to previous reports, we found that oxytocin was not related to patterns of functional connectivity between the amygdala and other brain regions. Conclusions Together, our results underscore the importance of considering individual differences in participants' endogenous oxytocin with respect to anxiety-related neural activity and neuromorphology.