BioProject

Adverse experiences in childhood are associated with altered hypothalamic pituitary adrenal axis function and negative health outcomes throughout life. It is now commonly accepted that abuse and neglect can alter epigenetic regulation of HPA genes. Accumulated evidence suggests harsh parenting practices such as spanking are also strong predictors of negative health outcomes. We predicted harsh parenting at 2.5 years old would predict HPA gene DNA methylation similarly to abuse and neglect, and cortisol output at 8.5 years old. Saliva samples were collected three times a day across three days to estimate cortisol diurnal slopes. Methylation was quantified using the Illumina Infinium MethylationEPIC array BeadChip (850K) with DNA collected from buccal cells. We used principal components analysis to compute a summary statistic for CpG sites across candidate genes. The first and second components were used as outcome variables in mixed linear regression analyses with harsh parenting as a predictor variable. We found harsh parenting significantly predicted methylation of several HPA axis genes, including novel gene associations with AVPRB1, CRHR1, CRHR2, and MC2R (FDR corrected p < 0.05). Further, we found NR3C1 methylation predicted a steeper diurnal cortisol slope. Our results extend the current literature by demonstrating harsh parenting may influence DNA methylation similarly to more extreme early life experiences such as abuse and neglect. Further, we show NR3C1 methylation is associated with diurnal HPA function. Elucidating the molecular consequences of harsh parenting on health can inform best parenting practices and provide potential treatment targets for common complex disorders. Overall design: Participants were recruited from state birth records for a longitudinal study investigating genetic and environmental influences on childhood health (Lemery-Chalfant et al. 2013). We recruited a sub-sample of monozygotic (MZ) twins (N = 96 individuals; 51% male; 50% Non-Hispanic White, 14.6% Hispanic/Latinx, 8.3% African American, 4.2% Asian American), Mage = 8.5 years, SD = .45. Seventy-one percent of primary caregivers reported currently being married and 91% were moms. Total household income ranged from $6,400 - $300,000 USD (M = $97,057, SD = $64,893) and 21% of families met Federal Medicaid Eligibility based on 2016 standards (Arizona Median Household Income = $53,510, US Census Bureau). Socioeconomic status (SES) was calculated as a mean composite of the family income, primary caregiver education level, and spouse/partner education level. All study procedures were approved by institutional review boards and are in accordance with the Helsinki Declaration of 1975.