The anxiety and aggression that result from social isolation have been traced to altered levels of an enzyme that controls production of a brain hormone.

People who experience chronically high levels of loneliness show gene-expression patterns that differ markedly from those of people who don't feel lonely, according to a new molecular analysis in the online open access journal Genome Biology.

Two University of Chicago psychologists, Louise Hawkley and John Cacioppo, have been trying to disentangle social isolation, loneliness, and the physical deterioration and diseases of aging, right down to the cellular level.