Loneliness and Isolation Linked to Years Lost to Depression and Anxiety

The work is an observational study in people. It used data from 277,489 adults in the UK Biobank who were free of seven major chronic diseases at the start: type 2 diabetes, cardiovascular disease, chronic respiratory disease, neurodegenerative disease, cancer, depression and anxiety. Because it observes people rather than assigning them to a treatment, it shows associations. It cannot show that loneliness or isolation caused the lost years.

The researchers, led by Lu Qi of Tulane University, separated two ideas that are often mixed up. Social isolation is an objective measure of how much social contact a person has. Loneliness is a subjective measure of how dissatisfied a person feels with the quality of their relationships. The two overlap, but they are not the same.

In the cohort, 3.3% of participants had loneliness only, 6.8% had isolation only, and 0.8% had both. Participants were followed for a median of about 13 to 14 years. Over that time there were 16,356 deaths and 78,829 new cases of the seven diseases.

The team estimated disease-free life expectancy at age 50. This is the number of years a person can expect to live without developing the listed conditions. People with both loneliness and isolation were compared with people who had neither.

For physical disease, women with both lived 2.4 fewer years free of the five physical diseases, and men lived 1.7 fewer years. For mental disorders, the gaps were larger. Women with both lived 3.7 fewer years free of depression and anxiety. Men lived 5.8 fewer years. All of these differences were statistically significant.

Across all seven conditions combined, women with both lived 3.0 fewer disease-free years and men 2.2 fewer. Loneliness alone and isolation alone were also linked to losses, though smaller ones. The gaps between groups narrowed with age. The results did not change appreciably when the researchers excluded people who became ill or died within two years, which helps guard against early illness driving the findings.

The study also asked whether a healthy lifestyle changes the picture. A healthier lifestyle was linked to more disease-free years in every group, lonely or not. But the loss tied to social isolation shrank substantially at higher lifestyle scores. In women, the mental-health loss tied to isolation was 2.2 years in the unhealthy-lifestyle group and 0.6 years in the healthiest group. That last figure was not statistically significant.

Loneliness did not follow that pattern. The loss tied to loneliness did not narrow significantly as lifestyle improved. Among women, for example, the mental-health loss linked to loneliness was 3.1, 2.6 and 4.2 years across unhealthy, middle and healthy lifestyle groups. In its coverage, ScienceDaily said habits such as diet, exercise, sleep and not smoking reduced the isolation-linked losses. The study's full lifestyle score is described in its supplementary material, which this summary does not cover.

The authors offer two possible explanations for the stronger mental-health link, and they say more research is needed. Earlier studies suggest mental health partly explains how loneliness and isolation affect physical disease. There is also substantial genetic overlap between loneliness and depression.

There are limits. Loneliness and isolation were measured at baseline, and the study cannot say which came first or whether they cause the outcomes. Qi told ScienceDaily the findings were not surprising, given earlier work linking isolation and loneliness to early death.

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What does this mean for personal health? Social connection looks like a factor tied to healthspan, the years lived in good health, and one that people can sometimes change. The results suggest healthy habits may help offset the cost of being isolated, but may not offset the cost of feeling lonely. That points to the quality of relationships, not only the amount of contact, as something to address directly. This study cannot say which approaches work.

Qi's team plans to study other population groups and to use clinical trials to test whether loneliness and isolation directly cause these health effects. Those trials are the next thing to watch.

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