Evidence for Skin-Deep Resilience Using a Co-Twin Control Design: Effects on Low-Grade Inflammation in a Longitudinal Study of Youth

Abstract This study tested the skin-deep resilience hypothesis – that low socioeconomic status (SES) youth who are working hard to succeed in life experience good psychological and educational outcomes but at a cost to their physical health – in a sample of monozygotic (MZ) twins. The National Longitudinal Study of Adolescent Health (Add Health) contained a sample of 226 MZ twin pairs at Wave 1 (M age=16 years), of whom 141 pairs completed the Wave 4 assessment 13 years later (M age=29 years). Family SES was measured at Wave 1 via income, education, and occupation. Conscientiousness was measured at Wave 4 as an indicator of those who were working hard to succeed in life. Outcomes measured at Wave 4 included low-grade inflammation (C-reactive protein, CRP), mental health (depression, problematic alcohol use), and academic success (educational attainment). A co-twin control design was utilized which directly compared within-twin differences in the association between conscientiousness and life outcomes. Main effects of between-twin conscientiousness were found such that higher levels of conscientiousness were associated with higher educational attainment, fewer symptoms of depression, and less problematic alcohol use, across all SES groups. An interaction between family SES and within-twin difference in conscientiousness was found for CRP, such that, among twins growing up in lower SES households, the twin with higher levels of conscientiousness had higher levels of CRP. These patterns provide support for the phenomenon of skin-deep resilience using a twin methodology that reduces the possibility of confounding by shared genetic and environmental factors.