There is growing interest in the role of the oxytocin system in social cognition and behavior. Peripheral oxytocin concentrations are regularly used to approximate central concentrations in psychiatric research, however, the validity of this approach is unclear. Here we conducted a pre-registered systematic search and meta-analysis of correlations between central and peripheral oxytocin concentrations. A search of databases yielded 17 eligible studies, resulting in a total sample size of 516 participants and subjects. Overall, a positive association between central and peripheral oxytocin concentrations was revealed [r = 0.29, 95% CI (0.14, 0.42), p < 0.0001]. This association was moderated by experimental context [Qb(4), p = 0.003]. While no association was observed under basal conditions (r = 0.08, p = 0.31), significant associations were observed after intranasal oxytocin administration (r = 0.66, p < 0.0001), and after experimentally induced stress (r = 0.49, p = 0.001). These results indicate a coordination of central and peripheral oxytocin release after stress and after intranasal administration. Although popular, the approach of using peripheral oxytocin levels to approximate central levels under basal conditions is not supported by the present results
Kemp, A.H., and Quintana D.S. (2017). Heart Rate Variability in Psychiatric Disorders, Methodological Considerations, and Recommendations for Future Research. In H.F. Jelinek, D.J. Cornforth, and A.H. Khandoker (Eds.), ECG Time Series Variability Analysis (pp. 327-343). Boca Raton, FL: CRC Press.