Loneliness is bad for you. When you’re disconnected, your immune system goes to hell. If we know that loneliness affects our immune response, it’s not surprising that it would happen at the level of DNA expression. Few higher mammals are solitary. Humans are relatively helpless as individuals in the natural world. Part of what makes us so powerful is that we’ve banded together in small groups. And part of the pain of loneliness is the recognition that without other people we simply can’t survive.