Loneliness triggers genetic changes that may cause early death

Loneliness is more than just a feeling - it triggers physiological changes which may cause illness and early death in older adults, a new study has claimed.
Perceived social isolation is a major health risk for older adults that can increase their risk of premature death by 14 per cent, researchers said.
Researchers have long known the dangers of loneliness, but the cellular mechanisms by which loneliness causes adverse health outcomes have not been well understood.
Now a team of researchers, including University of Chicago psychologist John Cacioppo, has shed new light on how loneliness triggers physiological responses that can ultimately make us sick.

The study shows that loneliness leads to fight-or-flight stress signalling, which can ultimately affect the production of white blood cells.
' The study examined loneliness in both humans and rhesus macaques, a highly social primate species. The human subjects were participants in the Chicago Health, Ageing, and Social Relations Study, a longitudinal study that began in 2002 with adults aged 50-68.

Previous research from this group had identified a link between loneliness and a phenomenon they called "conserved transcriptional response to adversity" or CTRA.
This response is characterised by an increased expression of genes involved in inflammation and a decreased expression of genes involved in antiviral responses.

Essentially, lonely people had a less effective immune response and more inflammation than non-lonely people.
For the current study, the team examined gene expression in leukocytes, cells of the immune system that are involved in protecting the body against bacteria and viruses.
As expected, the leukocytes of lonely humans and macaques showed the effects of CTRA - an increased expression of genes involved in inflammation and a decreased expression of genes involved in antiviral responses.
But the study also showed several important new pieces of information about loneliness' effect on the body.
First, the researchers found that loneliness predicted future CTRA gene expression measured a year or more later. Interestingly, CTRA gene expression also predicted loneliness measured a year or more later.

Leukocyte gene expression and loneliness appear to have a reciprocal relationship, suggesting that each can help propagate the other over time. These results were specific to loneliness and could not be explained by depression, stress or social support.
Next, the team investigated the cellular processes linking social experience to CTRA gene expression in rhesus macaque monkeys at the California National Primate Research Centre, which had been behaviourally classified as high in perceived social isolation.
Like the lonely humans, the "lonely like" monkeys showed higher CTRA activity. They also showed higher levels of the fight-or-flight neurotransmitter, norepinephrine.
The research appears in the journal PNAS.