Loneliness is commonly regarded as a social phenomenon in which individual personality differences contribute to its severity. Some people enjoy solitude, for example, because they never feel lonely, while people with high degrees of loneliness have shorter life expectancies than people who never feel lonely.

There may be more to it than that. Recent research shows that the gene expression in the immune cells of people with chronically high levels of loneliness is different than people who do not feel lonely. Even more telling, some genes were underexpressed in the same subjects, including those in antibody production.