This is discussed in the Limitations section of their article: https://jamanetwork.com/journals/jama/fullarticle/2677445 https://jamanetwork.com/journals/jama/f

This is discussed in the Limitations section of their article: https://jamanetwork.com/journals/jama/fullarticle/2677445 https://jamanetwork.com/journals/jama/fullarticle/2677445 > Third, despite adjusting for conditions that frequently precipitate wealth shocks, including marital disruption, unemployment, and a variety of health status and access to care indicators, residual confounding is likely. They adjusted for it, but maybe not enough.