Childhood separation experience predicts HPA axis hormonal responses in late adulthood: a natural experiment of World War II

Background: Animal models have linked early maternal separation with lifelong changes in hypothalamic-pituitary-adrenocortical (HPA) axis activity. Although this is paralleled in human studies, this is often in the context of other life adversities, for example, divorce or adoption, and it is not known whether early separation in the absence of these factors has long term effects on the HPA axis.

Aims: The Finnish experience in World War II created a natural experiment to test whether separation from a father serving in the armed forces or from both parents due to war evacuation are associated with alterations in HPA axis response to psychosocial stress in late adulthood.

Method: 282 subjects (M=63.5 years, SD=2.5), of whom 85 were non-separated, 129 were separated from their father, and 68 were separated from both their caregivers during WWII, were enlisted to participate in a Trier Social Stress Test (TSST), during which we measured salivary cortisol and, for 215 individuals, plasma cortisol and ACTH concentrations. We used mixed models to study whether parental separation is associated with salivary and plasma cortisol or plasma ACTH reactivity, and linear regressions to analyse differences in the baseline, or incremental area under the cortisol or ACTH curves.

Results: Participants separated from their father did not differ significantly from non-separated participants. However, those separated from both parents had higher average salivary cortisol and plasma ACTH concentrations across all time points compared to the non-separated group. They also had higher salivary cortisol reactivity to the TSST. Separated women had higher baselines in plasma cortisol and ACTH, whereas men had higher reactivity in response to stress during the TSST. Participants who had experienced the separation in early childhood were more affected than children separated during infancy or school age.

Conclusions: Separation from parents during childhood may alter an individual's stress physiology much later in adult life.