Loneliness can send a person down a path toward bad health, and even more intense loneliness, studies have shown. But while some have assumed the culprit was a dearth of others to remind a person to take care of himself or herself, new research suggests there’s a direct biological link between being lonely and ill health.

University of Chicago social psychologist John Cacioppo found loneliness is tied to hardening of the arteries (which leads to high blood pressure), inflammation in the body, and even problems with learning and memory. Even fruit flies that are isolated have worse health and die sooner than those that interact with others, showing that social engagement may be hard-wired, he said.