Psychiatrists are uncovering connections between viruses and mental health. They’re surprising.

When the Covid-19 pandemic hit, one of the biggest questions was: Why do some people get so much sicker than others? It’s a question that has forced researchers to confront some deep mysteries of the human body, and come to conclusions that have startled them.

By the fall of 2020, psychiatrists were reporting that among the many groups who were high risk, people with psychiatric disorders, broadly, seemed to be getting more severe forms of Covid-19 at a higher rate. Katlyn Nemani, an NYU neuropsychiatrist, decided to dig deeper, asking: Just how much...