US scientists may have uncovered a genetic reason why lonely people may have poorer health.
The UCLA research, published in Genome Biology, found certain genes were more active in people who reported feelings of social isolation. Many of the genes identified have links to the immune system and tissue inflammation - which may be damaging.
Other studies have shown clear links between lack of social support and illnesses such as heart disease. The researchers said that quality, not quantity, of friendships, appeared to be important.
The link between genes and loneliness has been explored before - a recent Dutch study of 8,000 twins also pointed to the connection. The UCLA research looked in more detail at which genes might be involved.
They took 14 volunteers and assessed their level of social interaction using a scoring system.
They then looked at genetic activity in their white blood cells and tried to compare the results.
In their "lonely" volunteers, various genes tended to be "over expressed" compared with those at the opposite end of the scoring scale.
Source - BBC