Animal studies suggest that maternal separation is associated with alterations in the hypothalamic–pituitary–adrenal (HPA) axis through effects that occur in a critical period following birth. Evidence for an association of the diurnal cortisol rhythm with maternal separation in humans is equivocal.

We examined whether maternal separation in childhood is associated with diurnal cortisol pattern in 3712 middle-aged men and women. Two aspects of cortisol release were examined: the cortisol awakening response (CAR) and the diurnal slope in cortisol throughout the day.

Maternal separation in childhood was reported by 12% of participants. Those participants who reported maternal separation had a larger CAR and flatter slopes in cortisol levels compared to those who did not report maternal separation [adjusted mean CAR in those reporting no separation versus separation: 7.1, 95% confidence interval (CI) 6.7–7.5 v. 8.4, 95% CI 7.3–9.5, p = 0.02, corresponding to adjusted mean diurnal slope: −0.129 (95% CI −0.130 to −0.128) v. −0.126 (95% CI −0.128 to −0.124), p = 0.01]. In participants who reported maternal separation, the age of separation was not associated with either cortisol measure (p = 0.11). The association between maternal separation and slope in cortisol secretion was largely explained by smoking behaviour and marital status at the time of sample collection whereas that of the CAR was explained by childhood psychosocial, material factors and adult health behaviours.

Our findings suggest that maternal separation in childhood is associated with alterations in the diurnal cortisol pattern in middle age. These associations are predominantly accounted for by adult circumstances and behaviours.