Off-label intranasal oxytocin use in adults is associated with increased amygdala-cingulate resting-state...

Intranasally administered oxytocin gained popularity as a hormone facilitating trust, cooperation, and affiliation. However, the long-term consequences of oxytocin use are not known. Given that intensive media attention and advertisements of the "love hormone" might lead to a new form of misuse, we conducted an online survey and identified 41 individuals with oxytocin misuse. Misuse will be proposed throughout the manuscript instead of the more accurate "off-label use" for reasons of simplicity. We compared the social functions of oxytocin users with that of 41 matched control volunteers. We administered the "Reading the Mind in the Eyes Test" (RMET) and the National Institute of Health (NIH) Toolbox Adult Social Relationship Scales (NIH-ASRS) to delineate affective "theory of mind" and real-life social functions, respectively. Resting-state functional brain connectivity analyses were also carried out. Results revealed no significant differences between individuals with oxytocin misuse and control participants on the RMET and NIH-ASRS. However, individuals with oxytocin misuse showed an increased connectivity between the right amygdala and dorsal anterior cingulate cortex relative to the control group. Higher estimated cumulative doses of oxytocin were associated with enhanced amygdala-cingulate connectivity. These results show that individuals who have self-selected for and pursued oxytocin use have increased amygdala-cingulate resting connectivity, compared to individuals who have not used oxytocin, despite the lack of differences in RMET and NIH-ASRS scores. Further longitudinal studies are warranted to investigate the cause-effect relationship between oxytocin use and brain connectivity.