Childhood IQ and adolescent health behavior

This study investigates whether cognitive ability in early childhood predicts adolescent health-related and risky behaviors, independent of schooling and socioeconomic background. Using longitudinal data from the Kindergarten cohort of the Longitudinal Study of Australian Children (LSAC), we link matrix reasoning scores from ages 6 to 10 to health behaviors at age 16/17. Behaviors include substance use, unsafe driving, nutrition, dental hygiene, and sleep. To reduce dimensionality and interpret behavioral patterns, we derive two composite indices via principal component analysis: a risk-taking index and a health habit index. We find that higher early-life IQ is consistently associated with lower risk-taking and better health habits in adolescence, even after adjusting for a comprehensive set of early life covariates including non-cognitive traits, parental health behaviors, family SES, and regional disadvantages. A Gelbach decomposition shows distinct patterns of confounding: for risk-taking, the attenuation of the IQ-health behavior association is primarily explained by parental health behavior and ethnocultural background; for health habits, socioeconomic disadvantage is more salient. Peer characteristics at age 14/15 explain a substantial share of the IQ-risk-taking relationship, suggesting social environments as potential pathways. Robustness checks using the Cinelli & Hazlett sensitivity framework indicate that the IQ-health habits association is substantively and statistically robust to unobserved confounding. We interpret these findings as support for the hypothesis that early-life IQ may be an important upstream factor of health inequalities before educational differentiation occurs.