  A case-control study is designed to help determine if an exposure is
associated with an outcome. However, since case-control studies are
retrospective, they are often subject to recall bias. Recall bias can occur
when study subjects do not remember previous events accurately. In this paper,
we first define the estimand of interest: the causal odds ratio (COR) for a
case-control study. Second, we develop estimation approaches for the COR and
present estimates as a function of recall bias. Third, we define a new quantity
called the \textit{R-factor}, which denotes the minimal amount of recall bias
that leads to altering the initial conclusion. We show that a failure to
account for recall bias can significantly bias estimation of the COR. Finally,
we apply the proposed framework to a case-control study of the causal effect of
childhood physical abuse on adulthood mental health.
