P.2.018 - Child’s oxytocin response to mother-child interaction: the contribution of child genetics and maternal behaviour

Abstract

Oxytocin is a nine amino-acid peptide hormone synthesized in the hypothalamus and stored in the neurohypophysis for further release into blood circulation. Its main peripheral target is the feminine reproductive system, having a primordial role in labour and the postpartum period [1]. It also has an important role in regulating child’s needs for bonding and protection from threats [1], and has been shown to respond to close interactions [2], though evidence across studies about how exactly it operates is not entirely consistent. In order to understand which factors can indeed affect OT levels in response to affiliative interactions we will follow Bartz and colleagues et al.’s (2011) approach regarding OT administration and social behaviour [3]. According to this perspective the oxytocin effects are constrained by an interaction between individual and contextual features. This interaction would explain why the effects of oxytocin in the social domain are often weak and/or inconsistent. In this study we explore whether endogenous oxytocin response can also be affected by this interaction by focusing on child’s OXTR genotype and maternal interactive behaviour, respectively as individual and environmental factors. Salivary OT levels of 88 Portuguese pre-schoolers were analysed prior to and following a mother-child interaction task, and child’s OXTR SNP rs53576 was genotyped. Maternal interactive behaviour was assessed during the task based on Ainsworth scales [4]. A hierarchical regression analysis was conducted to predict changes in child’s oxytocin. Child’s genotype (i.e., presence vs absence on the A allele), and maternal interactive behaviour were entered in the first step, to test for their main effects on child’s OT response. The next and final step included the 2-way interaction between the individual and environmental variables (OXTR genotype and maternal interactive behaviour, respectively). Results show an interaction effect of genotype (rs53576) by maternal interactive behaviour in relation to variation in child OT concentrations (B=0.084, SE=0.037, t=2.277, p=0.025). Follow-up analysis revealed that only in the presence of lower scores in maternal behaviour, the two genotypes significantly differ in OT change scores (t(36)=3.007, p=0.005), with OT levels increasing during the interaction for the G homozygotes, and diminishing for A carriers. The result that, for A carriers, the child’s OT levels decrease after the interaction with less responsive mothers, might be explained by such interaction being perceived by the child as less pleasant, rewarding and engaging. However, the fact that OT levels increase for G homozygotes might seem more intriguing. We propose that these results could be read in light of the framework considering OT as a biomarker for social distress, being released to seek affiliative contact, particularly in less supportive environments (as it is the case of less responsive mothers). The fact that it occurs among G carriers is in line with evidence showing that this genotype is more likely to seek social support [5] and thus possibly more likely to make affiliative efforts. Findings provide support for the notion that OT response is not uniform and that both individual and contextual characteristics should be considered for a deeper understanding of OT regulation.