From animal studies we know that early social deprivation can make the HPA axis behave differently . This might be happening through epigenetic modification of the glucocorticoid gene. In rodents, social deprivation up regulate the axis, while in primates it seem to be down regulating it. Normalising social stimulation is found to correct these changes.
What about human experience of early social deprivation? Many existing studies are confounded by the inability to separate social deprivation from physical deprivation, malnutrition etc. Koss et al reports the results of an interesting study addressing this question. Would HPA axis behave differently in adopted children? What factors ( i.e. pre adoptive care related) influence these changes? would these changes explain differences in problem behaviour ?
They compared children raised in families (53 children) with those adopted out of institutionalised care (66 children, 18 months- 36 months age at recruitment). A second comparison group comprised of children (50 children) adopted internationally from foster care.Children provided daily cortisol samples at roughly 2, 9, 17, and 25 months post-adoption.
The cortisol levels usually show a steep slope over the day time. Early deprivation and disruption resulted in a LESS steep cortisol SLOPE over the daytime hours. This was particularly strong with more social deprivation. This might be due to reduced cortisol awaking response. Adoption did not result in change in this. Parents reported significantly more problem behavior for those adopted from institutions and those from foster care and the daytime cortisol slope mediated this finding.
Limitations:This is a convenience sample and has its limitations
Conclusion: first longitudinal assessment of daily cortisol production in children as they adapt to their new families. Chronic stress early on in life may have long lasting effect on HPA axis. We need more understanding on the mechanisms that may have produced this type of down-regulation of the axis.
Summary of the article:
Koss KJ, Hostinar CE, Donzella B, Gunnar MR. Psychoneuroendocrinology. 2014 Aug 7;50C:1-13