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. …