Exploring the Heritability of Stress Hormones

All humans experience stress: physiological stress, mental stress, and even emotional stress. Stress can be short-term due to the activation of the sympathetic nervous system and the secretion of the hormones norepinephrine and epinephrine from the adrenal cortex. However, stress can be long-term as well. When the human body experiences long-term stress, the hypothalamic-pituitary-adrenal (HPA) axis is activated, leading to the release of cortisol from the adrenal cortex. Measuring the concentration of cortisol in hair is a widely accepted method of assessing long-term activation the HPA axis. In the field of neuroendocrinology, it is unclear whether activation of the HPA axis caused by stress is due to an individual’s genetics or an individual’s environment. In this study, in collaboration with Boston University, hair cortisol concentrations of five year old monozygotic twins will be compared to assess the similarity in cortisol concentrations between genetically identical individuals. Determining the heritability of cortisol has profound scientific and social implications. It is important to predict cortisol concentrations because a hyperactive or blunted HPA axis can lead to a multitude of disorders including cardiovascular disease, fatigue, anxiety and depression, and suppression of the immune system and inflammatory responses. The ability to predict cortisol concentrations may allow clinicians to directly combat the effects of a hyperactive or blunted HPA axis in children through the use of medications, life style changes, and even behavioral therapy.