Background: Adverse social determinants of health (SDoHs), specifically psychosocial stressors and material hardships, are associated with early childhood obesity. Less is known about whether adverse SDoHs modify the efficacy of early childhood obesity prevention programs. Methods: We conducted a secondary analysis of publicly insured birthing parent-child dyads with Latino backgrounds participating in a randomized controlled trial of the Starting Early Program (StEP), a child obesity prevention program beginning in pregnancy. We measured baseline adverse SDoHs categorized as psychosocial stressors (low social support, single marital status, and maternal depressive symptoms) and material hardships (food insecurity, housing disrepair, and financial difficulties) individually and cumulatively in the third trimester. Logistic regression models tested effects of adverse SDoHs on StEP attendance. We then tested whether adverse SDoHs moderated intervention impacts on weight at age 2 years. Results: We observed heterogeneous effects of adverse SDoHs on outcomes in 358 parent-child dyads. While housing disrepair decreased odds of higher attendance [adjusted odds ratio (aOR) 0.52, 95% confidence interval (CI): 0.29-0.94], high levels of psychosocial stressors doubled odds of higher attendance (aOR 2.36, 95% CI: 1.04-5.34). Similarly, while certain adverse SDoHs diminished StEP impact on weight (e.g., housing disrepair), others (e.g., high psychosocial stress) enhanced StEP impact on weight. Conclusions: Effects of adverse SDoHs on intervention outcomes depend on the specific adverse SDoH. Highest engagement and benefit occurred in those with high psychosocial stress at baseline, suggesting that StEP components may mitigate aspects of psychosocial stressors. Findings also support integration of adverse SDoH assessment into strategies to enhance obesity prevention impacts on families with material hardships. Trial Registration: This study is registered on clinicaltrials.gov: Starting Early Obesity Prevention Program (NCT01541761); https://clinicaltrials.gov/ct2/show/NCT01541761.
Keywords: early childhood obesity; intervention; nutrition; parenting; social determinants of health.