Loneliness leads to illness and early death

Loneliness is not just an emotional state of mind, it actually triggers genetic changes which cause illness and early death, a study shows for the first time.

Previous studies have found that social isolation is a major health problem that can increase the risk of premature death by 14 percent.

Now researchers at the University of Chicago and the University of California have discovered thatloneliness actually triggers physical responses in the body which make people sick.

It appears to trigger the ‘fight or flight’ stress signal which affects the production of white blood cells. It also increases activity in genes which produce inflammation in the body while lowering activity in genes which fight off illness, promoting high levels of inflammation in the body.

Essentially, lonely people had a less effective immune response and more inflammation than non-lonely people. They feel socially threatened which has an enormous impact on health.

John Capitanio, of the California National Primate Research Centre at the University of California, Davis said: “Perceived social isolation is a risk factor for chronic illness and all-cause mortality but the molecular mechanisms remain ill understood.

“In humans, loneliness involves an implicit hyper-vigilance for social threat.”

The study examined loneliness in both humans and rhesus macaques, a highly social primate species.

They found that loneliness predicted how active the CTRA gene was, even a year later and vice versa. People who had high gene activity were still lonely after 12 months. They also showed higher levels of the fight-or-flight neurotransmitter, norepinephrine.

Previous research has found that norepinephrine can stimulate blood stem cells in bone marrow to make more of a particular kind of immune cell (monocytes) which ramps up inflammation in the body.

Both lonely humans and monkeys showed higher levels of monocytes in their blood. In an additional study, monkeys repeatedly exposed to mildly stressful social conditions such as unfamiliar cage-mates also showed increases in monocyte levels.

The researchers also showed that, in monkeys at least, the lonliness changes allowed simian immunodeficiency virus (the monkey version of HIV) to grow faster in both blood and brain.

Finally, the researchers determined that this monocyte-related CTRA shift had real consequences for health. In a monkey model of viral infection, the impaired antiviral gene

The "danger signals" activated in the brain by loneliness ultimately affect the immune system, the researchers conclude, as they warn against living ‘chronically on the social perimeter.’

The research was published in the Proceedings of the National Academy of Scineces.

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