Loneliness, according to Stephanie Cacioppo, is the result of biological signals that push us to reach out to others interacting with a dysfunctional mind that perceives social danger everywhere. She’s focused on a promising intervention: a neurosteroid called pregnenolone, which has been shown to improve stress-related disorders and ease the hypervigilance in the brain that arises when a person is exposed to social threats. Cacioppo’s goal is not to make people stop feeling lonely altogether, but to interfere with the ways loneliness affects the brain and body....