A new study published in psychoneuroendocrinology revealed the potential connection between socioeconomic status in childhood and cortisol levels in adolescence. The research team tried to unravel the relationship between genetics and the environment, as each influences cortisol levels.
Their research revealed that cortisol levels, measured in hair samples from 19-year-old subjects, were only 39% heritable; the remaining 61% were due to environmental factors. Heritability refers to the degree to which 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 cortisol release.
Previous research has found that children living in or near poverty 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 that “children of lower socioeconomic levels (SES) are disproportionately exposed to chronic stressors in their daily lives, which can wear down their physiological stress systems and increase subsequent risks of psychopathology.” Previous research had been unable to determine how much cortisol activity was genetic and how much was the result of environmental stimuli; For Cantave and his colleagues, this became the focus of his 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 Can$30,000 per year.
For example, in the year 2000, a family of four earning less than CAD 35,000 was considered to be in poverty. Socioeconomic data was collected at different times from these families over 19 years. When the twins were 19 years old, hair samples were collected and tested 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 rather than genetic factors. 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 age 19, leading the research team to conclude that “the fact that SES in early childhood was still associated with elevated cortisol levels 14 years later , albeit indirectly, emphasizes the importance of implementing psychosocial interventions with the goal of either recalibrating youth’s HPA axis activity after early adversity or preventing the effects of later adversity on elevated cortisol levels.
Some recognized limitations include the absence of gender-specific data, and those potential differences may be relevant to therapeutic interventions. They were also unable to draw any conclusions about the timing of harmful environmental influences and the consequences for the HPA axis and cortisol levels. This information would be significant in determining what types of interventions would be useful at what stage of development.
The study, “Association between timing of familial socioeconomic deprivation and adolescent capillary cortisol among adolescent twins: a study of the genetic and environmental processes involved“, was written by Christina Cantave, Mara Brendgen, Sonia Lupien, Ginette Dionne, Frank Vitaro, Michel Boivin and Isabelle Ouellet-Morin.