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Loneliness can wreak havoc on our cells and increase our risk of heart disease, scientists warn.

A state of social isolation can affect the genes in our body by heightening our risk of inflammation and decreasing our immunity towards viral infection.

Humans are known to be social creatures. We crave companionship - to be surrounded by friends and share our personal experiences with others. It's in fact been a key to our survival.

But there is a trade-off. If companionship is necessary for survival, its opposite - seclusion - can be toxic.

Chronic loneliness can affect our cells by altering the way our genes respond to inflammation and fight viral infections, according to genetics researcher Dr Steve Cole

Loneliness has been associated with a number of health problems. It can affect mood disorders and trigger depression, but it has also been linked to heart disease, higher blood pressure, immunity function, and nervous system disorders.

A 2015 review study showed that both actual and perceived social isolation increased our chances of dying early by 26 percent.

In the UK and the US, approximately one in three people older than 65 live alone, and in the US, half of those older than 85 live alone. 

In both countries, studies show that loneliness in people older than 60 can reach as high as 46 percent. Because the 'baby boomer' population is larger than any other, by the year 2030, the majority of Americans will be 70 and older.

But researchers have been studying how loneliness affects us on also a cellular level. 

In 2007, Dr Steve Cole, a genetics researcher at the University of California Los Angeles, and a team of researchers discovered that the cells of people who have gone through periods of chronic loneliness look different.

In particular, the white blood cells of those sufferers appeared to be stuck in a 'state of fear'. Dr Cole and his colleagues observed two main genetic differences between lonely and non-lonely people.

The first was that the genes that code for the body's response to inflammation are turned on to a degree not seen in non-lonely people.

Dr Cole told Vox: 'Inflammation is great at responding to acute injury, but if you have inflammation going chronically, it serves as a fertilizer for chronic diseases like atherosclerosis and cardiovascular disease, neurodegenerative diseases, and metastatic cancer.

'That provides one reasonable biological explanation for why they might be at an increased risk for these diseases.'

The second difference was suppressed activity in a set of genes that typically fend off viral infections. 

Dr Cole says this is a biological trade-off. The inflammation response is how the body attacks bacteria. But our body's response to viruses can actually make bacteria thrive. Therefore, the body picks one over the other.

Our bodies' response to chronic loneliness isn't very different from our response to sources of chronic stress, which can vary from lifestyle choices such as a poor diet or a lack of sleep to living conditions such as low socioeconomic status or post-traumatic stress disorder.

Dr Cole said: 'You see the same general molecular pattern across a diverse range of bad human life circumstances.

'Loneliness activates the body's generic stress response.'

When we are stressed, our bodies release the hormones epinephrine and cortisol.

These hormones, when they enter the blood stream, can activate the genetic changes that affect our inflammation response and response to viral infections.  

Dr Cole and his team found in longitudinal studies that when feelings of loneliness decline, so do the cellular symptoms - but such interventions to reduce these symptoms are only 'modest'. 

He believes loneliness to be a silent epidemic and that it is actually a larger risk factor for disease than the more commonly studied anxiety and depression.

Because loneliness increases with age, there is fear of a new wave of loneliness as the largest percentage of Americans, the baby boomers, age.

Dr Cole said he started to get notes from 'lonely people being devoured by disease and suffering, both personal and somatic.

'There is a huge hidden epidemic of loneliness and disenfranchisement from the human race.'