Are all risks equal? Understanding the differential mechanism linking early environmental risk and obesity via the interplay of mental health and lifestyle factors.

Abstract

BACKGROUND The mechanisms linking early environmental risk (EER) and obesity via the interplay of mental health and lifestyle factors in the early life stage remain unclear. OBJECTIVE To examine whether EER was associated with later mental health, lifestyle factors and obesity and to identify the mediating roles of mental health and lifestyle in these relationships. METHOD Using data from the Millennium Cohort Study (valid n=5401), we longitudinally assessed the relationship between EER (prenatal risks, neonatal risks, low socioeconomic status, maternal psychological problems and harsh parenting; 9 months to age 3 years), mental health problems in childhood (internalising and externalising problems; age 7 years), lifestyle factors in early adolescence (diet, exercise, smoking and drinking; age 11 years) and obesity in late adolescence (age 14-17 years). Structural equation modelling was used to test proposed pathways. FINDINGS The proposed model showed an acceptable fit (Comparative Fit Index=0.926, Tucker-Lewis Index=0.875, root mean square error of approximation=0.034, standardised root mean square residual=0.046). EER was significantly associated with later mental health problems, lifestyle factors (ie, diet, exercise, smoking) and obesity. Higher EER was modestly associated with higher obesity risk via the interplay of externalising problems and drinking (β=0.01, p=0.036). The sex-stratified model results indicated differences between males and females. CONCLUSION By highlighting the importance of EER and the mediating role of lifestyle factors in mental health and later obesity risk, our findings provide evidence of shared risk mechanisms linking mental and physical health. CLINICAL IMPLICATIONS These findings suggest that integrating mental health assessment (especially externalising symptoms) with routine screening for adolescent alcohol use and other risk factors could inform more targeted obesity prevention in clinical and public health settings.