Lonely individuals are more likely to be sick, study finds

Recent research found that individuals who were socially disconnected—lonely, socially isolated, or lacking social support—had a higher incidence of all 11 categories of medical conditions tracked in a large Danish study. The increased risk was highest for mental disorders, with socially disconnected individuals facing a 2.63-times higher risk. The study was published in Epidemiology and Psychiatric Sciences.

It is quite straightforward that individuals who are ill often rely more heavily on others for support. When someone lacks a support system, navigating illness—and even surviving it—can become significantly more difficult. However, research suggests that social disconnectedness is not just a consequence of illness but also a potential cause of it. People with diminished social connections are at increased risk of developing a wide range of medical conditions.

These individuals appear to be more vulnerable to developing conditions such as depression, dementia, coronary heart disease, stroke, sarcopenia, and other chronic illnesses. Despite growing evidence, data on the full scope of this connection has been limited, partly because socially disconnected individuals are often harder to reach in large-scale studies.

To address this gap, study author Lisbeth Mølgaard Laustsen and her colleagues set out to provide a comprehensive analysis of both relative and absolute differences in the incidence of 11 broad categories of medical conditions, using three distinct measures of social disconnectedness: loneliness, social isolation, and low social support.

Loneliness refers to the subjective feeling of being alone or emotionally distanced from others—a distressing experience where one’s social relationships are perceived as lacking in quantity or quality. Social isolation, by contrast, is more objective, defined by a lack of social interactions or close contacts. Low social support involves having fewer people to rely on for emotional, informational, or practical help. This lack of support can significantly impair a person’s ability to cope with life’s challenges and health issues.

The researchers analyzed data from the Danish National Health Survey, linking survey responses to national health registers. The final analysis included 162,604 participants. Of these, 129,319 responded to the 2017 survey from four Danish regions (Central Denmark Region, North Denmark Region, Region Zealand, and the Capital Region of Denmark), while 33,285 participated in the 2013 survey from the Central Denmark Region. The average participant age was 48 years, and 51% were women.

As part of the survey, participants completed brief assessments of their social connections: the Three-Item Loneliness Scale for loneliness, a four-item scale for social isolation, and a single question about emotional support: “Do you have someone to talk to if you have problems or need support?” The researchers used these assessments to construct a composite measure that captured overall social disconnectedness.

These data were then linked to medical records tracking diagnoses across hospitals and outpatient, inpatient, and emergency settings. The researchers focused on 11 categories of medical conditions:

• Mental disorders
• All-cause dementia
• Circulatory conditions
• Endocrine conditions
• Pulmonary conditions
• Gastrointestinal conditions
• Urogenital conditions
• Musculoskeletal conditions
• Hematologic conditions
• Neurologic conditions
• Cancer

The results showed that lonely individuals were more likely to develop conditions in all 11 categories, compared to those who were not lonely. The strongest association was with mental disorders, where loneliness was linked to more than a threefold increase in risk.

Similarly, individuals classified as socially disconnected—based on the composite measure—had a 2.63-times higher risk of developing a mental disorder. While all other medical conditions also showed elevated risk, the magnitude was generally lower. The weakest associations were seen with cancer, where the results were more ambiguous and in some cases consistent with lower incidence rates.

When examining social isolation on its own, the picture became more complex. While isolated individuals were still at significantly higher risk for mental health conditions, they were at a slightly lower risk for neurologic conditions, and did not show increased risk for several categories, including musculoskeletal, gastrointestinal, and circulatory conditions.

“Our results expand existing evidence linking social disconnectedness to elevated risks of mental disorders, dementia, circulatory conditions and musculoskeletal conditions. Notably, we additionally found higher incidence rates of endocrine, pulmonary, gastrointestinal, urogenital, hematologic, and neurologic conditions and cancer although the estimates for cancer were also consistent with lower rates. Contrary to previous evidence, our findings suggest that loneliness is a stronger determinant for subsequent medical conditions than social isolation and low social support,” the study authors concluded.

The study sheds light on the links between social disconnectedness and health. However, it should be noted that the design of the study does not allow any causal inferences to be derived from the results. While it is possible that loneliness contributes to the development of medical conditions, it is also possible that people suffering from these medical conditions are less able to participate in social activities leading to loneliness and social disconnectedness.

The paper, “Social disconnectedness, subsequent medical conditions, and, the role of pre-existing mental disorders: a population-based cohort study,” was authored by L. M. Laustsen, M. Lasgaard, N. C. Momen, D. Chen, J. L. Gradus, M. S. Grønkjær, M. M. Jensen, and O. Plana-Ripol.