Loneliness is linked to poor physical and mental health, and is an even more accurate predictor of early death than obesity. To better understand who is at risk, researchers conducted the first genome-wide association study for loneliness -- as a life-long trait, not a temporary state. They discovered that risk for feeling lonely is partially due to genetics, but environment plays a bigger role.

Source: Do these genes make me lonely? Study finds loneliness is a heritable trait