The biological embedding of social adversity: How adolescent housing insecurity impacts inflammation over time

Background & Purpose: Adolescent housing insecurity is a dynamic form of social adversity that impacts child health outcomes worldwide. However, the means by which adolescent housing insecurity may become biologically embedded to influence health outcomes over the life course remain unclear. Therefore, we aimed to utilize life course perspectives and advanced causal inference methods to evaluate the potential for inflammation to contribute to the biological embedding of adolescent housing insecurity. Materials and methods: Using prospective data from the Great Smoky Mountains Study, we investigated the relationship between adolescent housing insecurity and whole -blood spot samples assayed for C -reactive protein (CRP). Adolescent housing insecurity was created based on annual measures of frequent residential moves, reduced standard of living, forced separation from the home, and foster care. Annual measures of CRP ranged from 0.001 mg/L to 13.6 mg/L (median = 0.427 mg/L) and were log 10 transformed to account for positively skewed values. We used g -estimation of structural nested mean models to estimate a series of conditional average causal effects of adolescent housing insecurity on CRP levels from ages 11 to 16 years and interpreted the results within life course frameworks of accumulation, recency, and sensitive periods. Principal Results: Of the 1,334 participants, 427 [44.3 %] were female. Based on the conditional average causal effect, one exposure to adolescent housing insecurity from ages 11 to 16 years led to a 6.4 % (95 % CI = 0.69 - 12.4) increase in later CRP levels. Exposure at 14 years of age led to a 27.9 % increase in CRP levels at age 15 (95 % CI = 6.5 - 53.5). Recent exposures to adolescent housing insecurity ( <3 years) suggested stronger associations with CRP levels than distant exposures ( >3 years), but limited statistical power prevented causal conclusions regarding recency effects at the risk of a Type II Error. Major Conclusions: These findings highlight inflammation -as indicated by increased CRP levels -as one potential mechanism for the biological embedding of adolescent housing insecurity. The results also suggest that adolescent housing insecurity -particularly recent, repeated, and mid -adolescent exposures -may increase the risk of poor health outcomes and should be considered a key intervention target.