The enduring impact of childhood experience on mental health: evidence using instrumented co-twin data

The question of whether there is a lasting effect of childhood experience on mental health has eluded causal measurement. We draw upon identical twin data and econometric instrumentation to provide an unbiased answer. We find that 55% of a one standard deviation change in mental health due to idiosyncratic experience at age 9 will still be present three years later. Extending the analysis, we find such persistence to vary with age at impact, gender, and mental health sub-categories. This investigation allows us to get a grasp on the degree to which childhood events influence health and socio-economic outcomes by way of their lagged effect on subsequent mental health. A better understanding of the evolution of mental health also helps identifying when mental health issues can be most effectively treated.