Inspired by this article, it occurs to me that, if they last for many more months, the coronavirus lockdowns will provide a test of the supposed causal link between loneliness and all-cause mortality:
In a review of prospective studies on social isolation and health, House et al. (3) confirmed that social isolation was a major risk factor for morbidity and mortality from widely varying causes—a risk factor comparable in size to obesity, sedentary lifestyles, and possibly even smoking. These effects were evident even after statistically controlling for known biological risk factors, social status, baseline measures of health, and health behaviors
My prior belief is that loneliness correlates with life expectancy for the same reason wealth with a society correlates with life expectancy, and that just as making a society suddenly less wealthy doesn’t lead to an increase in mortality, nor will moving the society’s bell curve of loneliness.