On the SARS-CoV-2 pandemic as a proposed instrumental variable

Diemer, Elizabeth W; Swanson, Sonja A

Dimitris and Platt (Am J Epidemiol. XXXX;XXX(XX):XXXX-XXXX) take on the challenging topic of using “shocks” such as the SARS-CoV-2 pandemic as instrumental variables to study the effect of some exposure on some outcome. Evoking our recent lived experiences, they conclude that the assumptions necessary for an instrumental variable analysis will often be violated and therefore strongly caution against such analyses. Here, we build upon this warranted caution while acknowledging that such analyses may still be pursued and conducted. We discuss strategies for evaluating or reasoning about when such an analysis may be clearly inappropriate for a given research question, as well as strategies for interpreting study findings with especial attention to incorporating plausible sources of bias in any conclusions drawn from a given finding.