New research suggests that it's not just the social situation you're in, but also the genes you're born with that affect your likelihood of feeling lonely.
While environmental factors definitely play a bigger role, a new study of more than 10,000 people has shown that loneliness can be partly hereditary too.
As loneliness feeds into all kinds of physical and mental health problems, and is a significant factor in early deaths, scientists are keen to understand more about where it comes from so that we can get better at preventing it.
Specifically, the team was interested in understanding if there could be a genetic risk factor for loneliness.
"We want to know why, genetically speaking, one person is more likely than another to feel lonely, even in the same situation," said lead researcher, psychiatrist Abraham Palmer, from the University of California, San Diego.
"For two people with the same number of close friends and family, one might see their social structure as adequate while the other doesn't," he added. "And that's what we mean by 'genetic predisposition to loneliness'."
The researchers pored through a longitudinal health study in the US of 10,760 people aged 50 and older to try and spot links between genetics and loneliness.
Based on that data, they estimated that 14 to 27 percent of the risk of lifetime loneliness could be genetic, which is actually lower than previous estimates based on smaller sample sizes, but still not an insignificant amount.
Loneliness itself wasn't actually mentioned in the survey taken by the participants, because people are often reluctant to own up to it.
Instead, participants were asked about how often they felt that they lacked companionship, how often they felt left out, and how often they felt isolated from others. The results were balanced to take account of age, gender, and marital status (as married people generally feel less lonely than single people).
The team also compared the DNA of the participants to look for any patterns between feelings of loneliness and certain genetic areas.
This was the first genome-wide association study for loneliness, and while the researchers weren't actually looking for specific gene variants linked to loneliness – that's their next aim, they say –they did find evidence that a genetic risk for loneliness was associated with neuroticism and depressive symptoms.
Palmer and his team have now come up with an early hypothesis that loneliness could be a biological warning system: an alarm that goes off in our bodies when we're not getting the social interaction we might need or want.
So why did previous studies find a higher genetic association with loneliness? It could be because of something called the chip heritability method - a technique used by the original team, where common genetic variations are examined rather than rare ones.
The fact that they focussed on people exclusively in the US might have also had an effect, according to the researchers of this newer study.
While there's more work to be done, the research adds to a growing body of evidence that suggests that some of us might be born with a tendency to feel lonelier than others. So why not give that old estranged friend of yours a call?
The results have been published in Neuropsychopharmacology.