Test for exclusion restriction in STATA when using IV?

[Sylvie Rod]

Hello,

I am using C-section as an instrumental variable to examine the causal effect of breastfeeding on child development. I’m wondering if there’s a specific test in STATA to assess whether the exclusion restriction is being violated or not.

Many thanks.

[George Ford]

C-section apparently affect breast feeding (mixed evidence), but there are studies that model child development as a function of C-section (https://www.nature.com/articles/s41598-017-10831-y) that include breastfeeding. Probably not a good instrument and you'll get pushback from reviewers.

Some hospitals have breast feeding programs if you can get that data. And the time of birth can affect breast feeding. So can multiple births, but that could affect development directly.

There is no direct test of the exclusion restriction (like parallel paths), but there are indirect methods.

https://pmc.ncbi.nlm.nih.gov/articles/PMC4799892/#:~:text=Although%20falsification%20tests%20in%20general,by%20potential%20confounders%20that%20might

https://www.sciencedirect.com/science/article/pii/S0304407621000439

[Sylvie Rod]

Thank you very much George. This is very helpful!