Abstract
Income inequality is associated with poor health and social outcomes. Negative social comparisons and competition may involve the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes in underlying some of these complex inter-relationships. Here we investigate brain maturation, indexed by age-related decreases in cortical thickness, in adolescents living in neighborhoods with differing levels of income inequality and household income. We examine whether inter-regional variations relate to those in glucocorticoid receptor (HPA) and androgen receptor (HPG) gene expression. For each sex, we used a median split of income inequality and household income (income-to-needs ratio) to create four subgroups. In female adolescents, the high-inequality low-income group displayed the greatest age-related decreases in cortical thickness. In this group, expression of glucocorticoid and androgen receptor genes explained the most variance in these age-related decreases in thickness across the cortex. We speculate that female adolescents living in high-inequality neighborhoods and low-income households may experience greater HPA and HPG activity, leading to steeper decreases in cortical thickness with age.
Highlights
The rising disparity in personal incomes among people living in the same geographic unit has led to a surge in research concerning the negative impact of this phenomenon on health outcomes
Cortical thickness decreases with age in both male and female adolescents
We have discovered that the age-related decreases in cortical thickness appear to be steeper in female adolescents living in neighborhoods with high inequality and households with low income
Summary
The rising disparity in personal incomes among people living in the same geographic unit (e.g., country or state) has led to a surge in research concerning the negative impact of this phenomenon on health outcomes. Psychosocial stress generated by individual’s perception of his/her position within the socioeconomic hierarchy mediates the negative health consequences of income inequality[9, 12, 13] Such social comparisons relate to less social cohesion and higher rates of mistrust within a society that may, in turn, increase individual levels of stress and anxiety[14]. Testosterone and cortisol appear to play a role in such age-related cortical thinning during this developmental period[27,28,29,30] These social, hormonal, and neurodevelopmental factors may help to explain the onset of some psychiatric disorders, such as depression and schizophrenia during adolescence and early adulthood[27, 31, 32]. There has been no investigation into the relationship between income inequality and brain development
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