A new study published in Psychoneuroendocrinology revealed the potential connection between socioeconomic status in childhood and cortisol levels in adolescence. The research team attempted to unravel the relationship between genetics and environment as each influences cortisol levels.
Their research revealed cortisol levels, as measured in hair samples in subjects 19 years of age, were only 39% heritable; the remaining 61% was due to environmental factors. Heritability refers to the degree to which the differences within groups of people can be attributed to genetic factors. These results indicate that socioeconomic status has long-term consequences for the functioning of the stress response system and its release of cortisol.
Prior research has found that children who live in poverty or close to it experience more health problems and are exposed to more long-term stress. There is evidence that these two factors are related. What is known as the hypothalamic-pituitary-adrenal (HPA) axis is the system that releases cortisol when stressful or dangerous situations occur.
Christian Cantave and colleagues state, “children from lower socioeconomic backgrounds (SES) are disproportionately exposed to chronic stressors in their daily lives, which may wear out their physiological stress systems and increase later risks for psychopathologies.” Earlier research had not been able to determine how much of cortisol activity was genetic and how much was a result of environmental stimuli; for Cantave and colleagues, this became the focus of their study.
Participants were 442 pairs of twins who were part of the Quebec Newborn Twin Study. The twins had joined the group in the late 1990s, and included 121 monozygotic (identical) twins and 261 dizygotic (fraternal) twins. Thirty percent of these twins had families that fell below 30,000 Canadian dollars per year.
For example, in the year 2000, a family of four making below CAD 35,000 was considered to be in poverty. Socioeconomic data were collected at different times from these families over the course of 19 years. When the twins were 19 years old, hair samples were collected and analyzed for cortisol levels.
Statistical analysis of the differences in cortisol levels in the monozygotic and dizygotic twin groups revealed that cortisol levels in late adolescence reflect environmental factors rather than genetics. In this case, 61% of the variation in cortisol levels was due to individual negative experiences.
The research found evidence of childhood socioeconomic status in cortisol levels at 19, leaving the research team to conclude, “the fact that early childhood SES was still associated with high cortisol 14 years later, even if indirectly, emphasizes the importance of implementing psychosocial interventions aiming to recalibrate youth’s HPA axis activity following early adversity or to prevent the effects of later adversity on high cortisol.”
Some acknowledged limitations include an absence of gender-specific data, and those potential differences may be relevant to therapeutic interventions. They also could not make any conclusions about the developmental timing of harmful environmental influences and the consequences for the HPA axis and cortisol levels. This information would be meaningful for determining what kinds of interventions would be useful at what developmental stage.
The study, “Association between the timing of family socioeconomic deprivation and adolescence hair cortisol among adolescent twins: A study of the genetic and environmental processes involved”, was authored by Christina Cantave, Mara Brendgen, Sonia Lupien, Ginette Dionne, Frank Vitaro, Michel Boivin, and Isabelle Ouellet-Morin.