On the Identification of Individual Principal Stratum Direct, Natural Direct and Pleiotropic Effects Without Cross-World Independence Assumptions

• Activity Number: 88 - SPEED: Causal Inference and Related Methodology Part 2
• Type: Contributed
• Date/Time: Sunday, July 28, 2019 : 5:05 PM to 5:50 PM
• Sponsor: Section on Statistics in Epidemiology
• Author(s): Jaffer Zaidi* and Tyler VanderWeele
• Companies: and Harvard University
• Keywords: Causal inference; mediation; direct effects; cross-world assumptions; experimental design

Abstract

The analysis of natural direct and principal stratum direct effects has a controversial history in statistics and causal inference as these effects are commonly identified with either untestable cross-world independence or graphical assumptions. This paper demonstrates that the presence of individual level natural direct and principal stratum direct effects can be identified without cross-world independence assumptions. We also define a new type of causal effect, called pleiotropy, that is of interest in genomics, and provide empirical conditions to detect such an effect as well. We apply our methods to reinvestigate the birth-weight paradox, in which babies born with low birth weight to mothers that smoked cigarettes were less at risk for infant mortality than babies born with low birth weight to mothers that did not smoke.