Feeling lonely and having few social connections are often talked about as the same thing. A large new study suggests they aren't, and that each is linked to fewer years of life free from depression, anxiety and physical illness.

The research, led by Professor Lu Qi at Tulane University's School of Public Health and Tropical Medicine, was published in Nature Communications. It followed 277,489 adults aged 40 to 69, all of whom were free of seven major conditions when the study began: diabetes, heart disease, lung disease, dementia, cancer, depression and anxiety.

Loneliness and isolation are measured differently

The researchers treated the two as separate things:

  • Social isolation is an objective measure of how much social connection a person has.
  • Loneliness is subjective: how dissatisfied someone is with the quality of their relationships, regardless of how social they actually are.

So a person can be surrounded by people and still feel lonely, or spend a lot of time alone without feeling lonely.

What the study found

Compared with people who had neither, people who were both lonely and socially isolated had fewer years free of disease from age 50:

  • Depression and anxiety: about 5.8 fewer years free of these conditions for men, and about 3.7 fewer years for women.
  • Physical disease: 1.7 fewer years free of major physical disease for men, and 2.4 fewer years for women.

"Overall, the study found that social isolation and loneliness can have a significant impact on disease-free life expectancy," Qi said. "This includes both physical and mental disease." He added that the results suggest "men are more susceptible to being affected by loneliness."

Healthy habits helped with one, not the other

The team also looked at lifestyle: diet, exercise, sleep and not smoking. A healthier lifestyle measurably narrowed the loss of disease-free years linked to social isolation. It did not significantly reduce the added risks linked to loneliness.

That difference matters. It suggests the two may need different kinds of support: more social contact may help someone who is isolated, while loneliness, which is about how relationships feel, may not be fixed by activity or healthy routines alone.

What the study can't tell us

This was an observational study. It shows a link between loneliness, isolation and fewer healthy years, but it can't prove that loneliness or isolation caused the difference. Other factors may play a part. The researchers say future work will use clinical trials to test whether the link is causal.

The figures are averages across a very large group. They don't predict what will happen to any individual.

If this sounds familiar

The study didn't test ways to reduce loneliness, so these are general ideas rather than findings from the research:

  • Notice whether you're short of contact (isolation), unhappy with the contact you have (loneliness), or both. They can need different things.
  • Small, regular contact, such as a weekly call, a class or volunteering, is often easier to keep up than a big social push.
  • If loneliness is affecting your mood or sleep, talking to a doctor or counsellor can help.

If you'd like to reflect on how connected you feel, MindBearing's Loneliness Test takes about two minutes. It's a self-reflection tool, not a diagnosis.