New evidence on the relationship between mental and physical health

Past research has documented that mental health has a causal impact on physical health. This represents a local average treatment effect, but policymakers are primarily interested in mental health changes for the entire population, not just those exposed to an arbitrary exogenous shock. The need for reliable quantitative evidence presents a notable empirical challenge. To fill this research void, we use a recent method proposed by Oster (2019) to assess the reliability of the instrumental-variable estimates. Our findings support the soundness of the instrumental-variable estimates in the present context, meaning that researchers can have a good degree of confidence in using such estimates for policy formulation.