OBJECTIVES: The neuroactive hormone oxytocin (OT) has significant influence on human behavior, and it has been measured peripherally in venous blood and in saliva in many behavioral neuroscience studies. Assessment of salivary hormone levels is popular due to non-invasiveness, but there is a controversy as to whether OT can be reliably measured in saliva and how possible time lags between plasma and salivary OT levels influence correlation.
DESIGN AND METHODS: In order to shed light on the question whether salivary and plasma OT levels correlate, we designed an experiment where healthy young men had to look at a presentation of trustworthy faces on a computer screen (faces were taken from an established database in trust research). During three points in time, plasma and saliva samples were collected and analyzed using ELISA.
RESULTS: Plasma and salivary OT levels did not correlate even when considering a time lag of 15 or 30 minutes.
CONCLUSIONS: Our results suggest that plasma and salivary OT levels do not correlate in healthy young men, and hence comparison of results across plasma and salivary studies is neither informative nor warranted. However, we recommend replicating this study based on mixed-gender samples.