Characterizing Biological Associations with Social Experiences

Early social experiences are associated with long lasting effects in physiology, development, health, and wellbeing. One potential explanation of this is the “biological embedding” of these experiences into an individual’s molecular landscape. This can relate to later expressions of vulnerability and resilience (reviewed in Merrill, Gladish & Kobor, 2019 Current Topics in Behavioural Neurogenomics and Gladish, Merrill & Kobor, 2022 Current Environmental Health Reports). Due to the temporal and experiential plasticity, and the chemical stability of DNAm, this molecular tag provides a fruitful avenue to examine how social environments can get “under the skin”. In collaboration with Dr. Nicole Letourneau and the Alberta Pregnancy Outcomes and Nutrition (APrON) cohort, we discerned and compared the DNAm of secure attachment, often associated with effective and sensitive caregiving, with insecure attachment styles as determined by the Strange Situation Procedure (Merrill, 2021, Attachment and Human Development).

During Dr. Merrill’s doctoral training at Cornell University with Dr. Cindy Hazan, she discovered her passion for attachment. She views attachment as a dynamic, biologically based system. A system that motivates individuals to seek proximity to their caregiver to ensure their safety, resulting in a relatively persistent pattern of interpersonal behavior. They found that children with attachment that reflected a positive social environment had differential DNAm regions associated with immune function and propagation of immune cells, as well as cognitive development and long-term potentiation.

An in-preparation follow-up to these findings was done in a different tissue, buccal epithelial cells from cheek swabs. The study examined disorganized attachment, often associated with fear of a caregiver. This reflected the current literature on adverse early environment and includes overlapping findings with studies on child maltreatment, child labor camps, and a replication of our findings with retrospective accounts of childhood trauma in the cheek swabs of 18-year-olds in the Wisconsin Study of Families and Work cohort. We hope our follow up with the APrON children, now age 14, will allow us to investigate if these biological signals of childhood maltreatment and associated behavioral patterns are maintained into adolescence. Additionally, how we can examine social environments from an epigenetic lens comes from a different collaboration with Dr. Letourneau.

We examined paternal adverse childhood events (ACEs), and the signal of this early adversity in the DNAm in their infant offspring. We found the differences in infant DNAm that associated with more paternal ACEs also related to sleep latency. This potentially indicates a biological transmission of trauma through disrupted sleep patterns. Further, to demonstrate the interaction of parenting, sleep, and DNAm, we are currently investigating the association of sleep and caregiver relationship with DNAm in children from the Conditions Affecting Neurocognitive Development and Learning in Early Childhood (CANDLE) cohort. This is a unique Memphis longitudinal birth cohort, in collaboration with Dr. Nicole Bush and Dr. Alicia Smith.

This work and future studies stemming from our findings will demonstrate a clearer picture of the molecular associations with parenting experiences across the lifespan.