Health shocks, recovery and the first thousand days: the effect of the Second World War on height growth in Japanese children

This paper uses the health shock of the Second World War on Japanese civilians to understand the effects of health shocks at different developmental stages on children’s long-run growth pattern and to test whether recovery is possible after an early life health shock. We construct a prefecture-level dataset of mean heights of boys and girls from ages six to nineteen from 1929 to 2015. Linking the heights recorded at different ages for the same birth cohort, we measure a counterfactual causal effect of the health shocks during the Second World War on the cohort growth pattern of children. We find that the war effect was greatest for cohorts exposed to the war in late childhood and adolescence: these cohorts were 1.7-3.0 cm shorter at adulthood and had delayed pubertal growth and slower maturation than they would have had if the war had never occurred. However, there were not persistent health penalties for children exposed to the war in early life, suggesting that catch-up growth was possible as health conditions improved after the war. These findings challenge the thousand-days consensus that children cannot recover from nutritional shocks in early life and indicate that adolescence is a sensitive period for health shocks.