Severe social and emotional deprivation in early life is written into our biochemical stress responses. That’s the latest learning from the long-running Bucharest Early Intervention Project (BEIP), which began in 2000 and has been tracking severely neglected Romanian children in orphanages. Some of these children were randomly picked to be placed with carefully screened foster care families, and they’ve been compared with those left behind ever since.
While studies in rodents have linked early-life adversity with hyper-reactivity of the sympathetic nervous system and the hypothalamic–pituitary–adrenal (HPA) axis, the relationship has been harder to pin down in humans. BEIP’s study, involving almost 140 children around the age of 12, had children perform potentially stressful tasks, including delivering a speech before teachers, receiving social feedback from other children and playing a computer game that malfunctioned partway through.
Unlike the rodents, the institutionalized children had blunted responses in the sympathetic nervous system, which is associated with the “fight or flight” response, and in the HPA axis, which regulates production of the stress hormone cortisol. The researchers note that this dulled physiologic response has been linked to health problems, including chronic fatigue, pain syndrome and auto-immune conditions, as well as aggression and behavioral problems.
The hopeful news from the study, published in this week’s Proceedings of the National Academy of Sciences, is that quality foster care can reverse these effects. In these fortunate children, stress responses approximated those of non-institutionalized children—but only if they were placed before the age of 2.
According to the researchers, this indicates a “sensitive period” during early life when caregiving environments exert a particularly strong influence on children’s stress response systems. “The early environment has a very strong impact on how the stress response system in the body develops,” said lead author Katie McLaughlin, PhD, a professor of psychology at the University of Washington, in a press release. “But even kids exposed to a very extreme negative environment who are placed into a supportive family can overcome those effects in the long term.”
Why did the BEIP researchers find a blunted stress response, while studies in rodents have found a hyperactive response? According to McLaughlin, it’s difficult to say for certain. It’s possible that since the institutionalized children had endured such extreme stress early in life, the tasks the researchers had them do were too benign to evoke much of a response.
Or it may be that their stress response systems were hyperactive at earlier points in development, then adapted by reducing the number of receptors in the brain that stress hormones bind to. “If we’d been able to measure their stress systems early in life, we would expect to find very high levels of stress hormones and stress reactivity,” McLaughlin said.
Another possibility is that humans and animals are simply different. The researchers write:
The complex nature of human attachment and social interaction with caregivers might be one domain in which direct parallels with the animal literature are limited, potentially related to the fact that the attachment relationship between children and caregivers is a necessary scaffold for development of numerous uniquely human capacities, including emotion regulation and language.
Though children in Romanian orphanages are a unique population, there could be implications for all children growing up amid neglect and social deprivation. The children involved in the study are now about 16 years old, and researchers next plan to investigate whether puberty has an impact on their stress responses. Puberty might represent another sensitive period when stress response systems are particularly tuned to environmental inputs.
BEIP investigator Charles A. Nelson, PhD, of Boston Children’s Hospital was a senior author on the paper. Read more on the project’s previous findings: