Scientists have discovered that lonely people tend to die earlier because they have a weaker immune system.

Researchers from the University of Chicago say people who do not have frequent interaction with others are 14 percent more likely to die early because they appear to have much lower levels of white blood cells in their body, according to the Mirror UK. The cells are extremely important because it is the human body's weapon for battling diseases and illnesses.

University scientists earlier conducted a similar study and discovered a link between loneliness and a phenomenon called conserved transcriptional response to adversity (CTRA).

CTRA is described as the effect of lonely people tending to have a weaker immune system response than those with a healthy social life. This occurs when the number of genes involved in inflammation increases and the amount of genes involved in antiviral responses falls.

In fact, loneliness can predict CTRA gene expression over a year later, since loneliness and leukocyte genes, which are cells responsible for protecting people against bacteria and viruses, tend to "provoke each other over time."

The scientists also conducted research on monkeys, and they discovered that lonely primates showed higher CTRA activity. Lonely monkeys as well as humans also have higher levels of monocytes in their blood samples, which could lead to serious health risks.

"Taken together, these findings support a mechanistic model in which loneliness results in fight-or-flight stress signalling, which increases the production of immature monocytes, leading to up-regulation of inflammatory genes and impaired anti-viral responses," said Professor John Cacioppo.

"The 'danger signals' activated in the brain by loneliness ultimately affect the production of white blood cells," he added. "The resulting shift in monocyte output may both propagate loneliness and contribute to its associated health risks."