Aaradhana Natarajan, 2020

The hypothalamus-pituitary-adrenal axis, or HPA axis, is a neuroendocrine pathway that is linked to emotional functioning and health. Researchers at the University of Maryland College Park, led by Dr. Stephanie Merwin, recently investigated whether or not the HPA axis functioning of a child showed correlation to that of their parents. They accounted for both the child’s temperament and parent’s psychological history in their analysis.

The researchers used saliva samples taken immediately after waking, 30 minutes after waking, and 45 minutes after waking to assess whether the fluctuations in morning cortisol would show correlations. Samples were obtained from parents and their children, aged 3-5 years. The study controlled for parents with non-depressive disorders and individuals taking drugs that would affect baseline cortisol. As a result, only 136 of the original 175 parent-child dyads was considered during data analysis. The parent’s psychological history was assessed using a semi-structured telephone interview in accordance with DSM-IV criteria. Child temperament was assessed through eight standardized behavioral assessments held in the laboratory. The assessment placed them on a scale of negative to positive emotionality, with the former indicating more behaviors typical of anxiety and irritability, while the latter indicated greater frequency of behaviors typical of joy and sociability.

Results supported the initial prediction of significant adrenocortical concordance. As parent’s average morning cortisol levels increased, so did those of their children. Dyads with children who demonstrated high negative emotionality also showed positive correlation in cortisol levels. Interestingly, higher levels of negative emotionality significantly correlated to lower morning cortisol levels in parents, while higher levels of positive emotionality significantly correlated to lower morning cortisol levels in the children.

The prediction that parental history of depression would correspond to greater parent-child concordance was also supported. A history of depression showed significant correlation to lower morning cortisol levels in parents, a correlation which was then extended to the lower cortisol levels in their children. The researchers hypothesized that possible disruption in parenting that may result from parental depression may facilitate disruptions in the child’s stress response, leading to the similarities in reduced cortisol level. However, the reduction in cortisol levels was greater in dyads where the children showed high levels of negative emotionality. Due to the structure of the study, the researchers were not able to find definite directionality, but they conclude that the interplay is likely bidirectional, with the temperament of the child affecting the dyad as much as the parent’s depressive history.

The results were consistent even after correlating for annual family income, sex of the child, and race.

It is also important to note that the majority of parents in the study were mothers. As there are significant differences in cortisol levels between males and females, this might be an area for further research. Similarly, further studies could address the impact of parent and child risk factors in a more longitudinal manner. Such research can lead to improvements in intervention protocols and early assistance for children at risk of HPA maladjustment, potentially reducing the occurrence of depressive disorders.

Sources:

1. Merwin, S. M., et al. (2017). Parent-child adrenocortical concordance in early childhood: The moderating role of parental depression and child temperament. Biological Psychology, 124, 100-110.
2. Image retrieved from: https://www.pexels.com/photo/hands-carrying-child-father-27118/