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Social connection

Meta-analyses of cohorts link social isolation and loneliness to more deaths, about 14% to 32% higher risk, and to more heart disease, stroke and dementia. Stronger social relationships were linked to 50% higher odds of survival. Loneliness is linked to depression. Trials found programs reduced loneliness modestly, most when they addressed how people think about social situations.

Checked 2026-11-13
Status
A daily life factor, not a product.
Also called
loneliness, social isolation, social relationships, social support, social ties, social network, friendship, community, living alone, social engagement, social integration, staying social
Studied for
living longer, heart health, stroke prevention, dementia prevention, memory, mood, depression, blood pressure, wellbeing

Strong several reviews agree · Moderate one review or consistent trials · Limited one or a few small studies · Untested no study in people, listed with what it rests on

Shown to help6

Reported risks0

No risks sourced yet.

What it was studied for, and what was found

Shown to help6

Strong

Death from any cause

Linked to higher death rates with social isolation and loneliness in three meta-analyses, about 14% to 32% higher, and 50% higher odds of survival with stronger relationships.

Compared with people with weaker social relationships [1]; people who were not socially isolated, lonely or living alone [2]; people who were not socially isolated or lonely [3]

The numbers and sources
Effect
People with stronger social relationships had 50% higher odds of survival (OR 1.50, 95% CI 1.42 to 1.59), consistent across age, sex, initial health, cause of death and follow-up. The link was strongest for complex measures of social integration (OR 1.91) and weakest for living alone versus with others (OR 1.19, 95% CI 0.99 to 1.44) [1]. In studies adjusting for confounders, social isolation (OR 1.29), loneliness (OR 1.26) and living alone (OR 1.32) were each linked to higher mortality, with no difference between objective and felt isolation [2]. In 90 cohorts, social isolation (1.32, 95% CI 1.26 to 1.39) and loneliness (1.14, 95% CI 1.08 to 1.20) were linked to all-cause mortality, and both to cancer mortality [3].
Population
308,849 participants in 148 studies [1]. Studies from 1980 to 2014 [2]. 2,205,199 adults in 90 prospective cohorts [3].
Sources
[1], [2], [3]
Caveats
Observational. Illness can cause isolation and loneliness, which is reverse causation, and initial health status changed the results in one review [2]. Social ties also shape smoking, activity and use of medical care, which may carry part of the link. The links were stronger in samples younger than 65 [2].
Strong

Heart disease and stroke

Linked to about 29% more coronary heart disease and 32% more stroke with poor social relationships, and 34% more cardiovascular deaths with social isolation, in two meta-analyses.

Compared with people with better social relationships [4]; people who were not socially isolated [3]

The numbers and sources
Effect
Poor social relationships were linked to new coronary heart disease (RR 1.29, 95% CI 1.04 to 1.59) and stroke (RR 1.32, 95% CI 1.04 to 1.68), with no difference by gender [4]. Social isolation was linked to cardiovascular mortality (1.34, 95% CI 1.25 to 1.44), and to all-cause mortality in people who already had cardiovascular disease (1.28) [3].
Population
16 longitudinal datasets in high-income countries with 4,628 heart disease and 3,002 stroke events over 3 to 21 years [4]. 2,205,199 adults in 90 cohorts [3].
Sources
[4], [3]
Caveats
Observational. The lower confidence limits sit close to no difference [4]. Early heart disease can limit social life before diagnosis.
Strong

Dementia and thinking in later life

Linked to more dementia with low social participation and contact in two meta-analyses. Loneliness was linked in one and not significantly in the other.

Compared with people with more social participation and contact and less loneliness [5]; people with better social engagement [6]; people with more social activity and larger social networks [7]

The numbers and sources
Effect
Low social participation (RR 1.41, 95% CI 1.13 to 1.75), less frequent social contact (RR 1.57) and more loneliness (RR 1.58, 95% CI 1.19 to 2.09) were linked to new dementia. Low satisfaction with one's social network was not (RR 1.25, 95% CI 0.96 to 1.62) [5]. A poor social network (RR 1.59, 95% CI 1.31 to 1.96) and poor social support (RR 1.28) were linked to dementia, and loneliness was not significantly linked (RR 1.38, 95% CI 0.98 to 1.94). Over 10 years or more, good social engagement went with 12% lower risk (RR 0.88) [6]. More social activity and larger networks were linked to better later-life thinking, a small association (r 0.054, 95% CI 0.043 to 0.065) [7].
Population
19 cohort studies in the general population [5]. 2,370,452 participants in 31 cohort and 2 case-control studies [6]. 51 longitudinal studies [7].
Sources
[5], [6], [7]
Caveats
Observational. Dementia changes behavior for years before diagnosis, so withdrawal from social life may be an early sign rather than a cause. Measures of social life varied widely between studies [7].
Moderate

Depression

Linked to more depression with loneliness, a moderate effect in one meta-analysis of 88 studies and a positive link in all ten longitudinal studies of older adults in a review.

Compared with people with lower loneliness scores [8]; less lonely older adults [9]

The numbers and sources
Effect
Loneliness had a moderate, significant effect on depression across 88 studies, unchanged by sample, publication type or year [8]. All 10 longitudinal studies in older adults found loneliness linked to later depressive symptoms, with odds ratios from 0.41 to 17.76 [9].
Population
40,068 people in 88 studies [8]. Older adults in 10 longitudinal studies [9].
Sources
[8], [9]
Caveats
Most of the larger review's studies measured both at one time, and its abstract gives no pooled size [8]. Depression also makes people withdraw and feel lonely, so the direction runs both ways. The longitudinal review did not pool its results [9].
Limited

Blood pressure

One cohort of 229 adults aged 50 to 68 found loneliness at the start predicted larger rises in systolic blood pressure over the next 4 years.

Compared with less lonely people in the same cohort [10]

The numbers and sources
Effect
Higher loneliness at the start predicted increases in systolic blood pressure 2, 3 and 4 years later, cumulatively, independent of age, sex, ethnicity, cardiovascular risk factors, medications, depressive symptoms, social support, perceived stress and hostility [10].
Population
229 White, Black and Hispanic adults aged 50 to 68 in Chicago, tested yearly for 5 years [10].
Sources
[10]
Caveats
One small observational cohort, and the test was one-tailed at p < .05 [10].
Strong

Programs to reduce loneliness

Shown to reduce loneliness modestly in pooled randomized trials. Programs addressing how people think about social situations had the largest effects, and added chances to socialize did not.

Compared with control groups in randomized comparison studies [11]; control groups [12]; control groups in randomized trials, some without active controls [13]

The numbers and sources
Effect
In 20 randomized studies, interventions reduced loneliness by a small mean effect size of -0.198 (95% CI -0.32 to -0.08). Social cognitive training had the largest effect (-0.598), social support programs a smaller one (-0.162), and programs adding chances to socialize (-0.062, p = 0.67) or teaching social skills (0.017) showed none [11]. Psychological interventions, most often cognitive behavioral therapy, reduced loneliness against control groups (g 0.43) [12]. In older adults, most interventions had small effects, and the evidence was rated very low in quality [13].
Population
50 interventions, 20 randomized [11]. 3,039 participants in 28 randomized trials across ages [12]. 4,592 adults aged 55 to 100 in 44 trials [13].
Sources
[11], [12], [13]
Caveats
Heterogeneity was considerable [12][13]. Pre-post and non-randomized studies gave larger effects than randomized ones [11]. These trials measured loneliness, not death, heart disease or dementia.

Amounts studied

Cohorts measured social ties in several ways: complex measures of social integration, network size, frequency of contact, participation in activities, living alone, and felt loneliness on scales such as the UCLA Loneliness Scale [1][5][11]. Objective isolation (few contacts, living alone) and subjective loneliness were analyzed separately and gave similar links to death [2]. Follow-up ran from 3 to 21 years for heart disease [4]. Loneliness programs were mostly face to face, group-based and weekly [12].

Claims tested and not found

  1. That more chances to socialize, on their own, reduce loneliness. In randomized studies, programs adding opportunities for social contact did not reduce loneliness (mean effect size -0.062, p = 0.67) [11].
  2. That low satisfaction with one's social network is linked to dementia. It was not significantly linked to new dementia (RR 1.25, 95% CI 0.96 to 1.62) [5].
  3. That social skills training reduces loneliness. Two randomized social skills interventions showed no reduction (mean effect size 0.017, p = 0.90) [11].

Sources

  1. Holt-Lunstad J, Smith TB, Layton JB. Social relationships and mortality risk: a meta-analytic review. PLOS Medicine. 2010. https://doi.org/10.1371/journal.pmed.1000316
  2. Holt-Lunstad J, Smith TB, Baker M, et al. Loneliness and social isolation as risk factors for mortality: a meta-analytic review. Perspectives on Psychological Science. 2015. https://doi.org/10.1177/1745691614568352
  3. Wang F, Gao Y, Han Z, et al. A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality. Nature Human Behaviour. 2023. https://doi.org/10.1038/s41562-023-01617-6
  4. Valtorta NK, Kanaan M, Gilbody S, et al. Loneliness and social isolation as risk factors for coronary heart disease and stroke: systematic review and meta-analysis of longitudinal observational studies. Heart. 2016. https://doi.org/10.1136/heartjnl-2015-308790
  5. Kuiper JS, Zuidersma M, Oude Voshaar RC, et al. Social relationships and risk of dementia: A systematic review and meta-analysis of longitudinal cohort studies. Ageing Research Reviews. 2015. https://doi.org/10.1016/j.arr.2015.04.006
  6. Penninkilampi R, Casey AN, Singh MF, Brodaty H. The Association between Social Engagement, Loneliness, and Risk of Dementia: A Systematic Review and Meta-Analysis. Journal of Alzheimer's Disease. 2018. https://doi.org/10.3233/JAD-180439
  7. Evans IEM, Martyr A, Collins R, et al. Social Isolation and Cognitive Function in Later Life: A Systematic Review and Meta-Analysis. Journal of Alzheimer's Disease. 2019. https://doi.org/10.3233/JAD-180501
  8. Erzen E, Çikrikci Ö. The effect of loneliness on depression: A meta-analysis. International Journal of Social Psychiatry. 2018. https://doi.org/10.1177/0020764018776349
  9. Van As BAL, Imbimbo E, Franceschi A, et al. The longitudinal association between loneliness and depressive symptoms in the elderly: a systematic review. International Psychogeriatrics. 2022. https://doi.org/10.1017/S1041610221000399
  10. Hawkley LC, Thisted RA, Masi CM, Cacioppo JT. Loneliness predicts increased blood pressure: 5-year cross-lagged analyses in middle-aged and older adults. Psychology and Aging. 2010. https://doi.org/10.1037/a0017805
  11. Masi CM, Chen HY, Hawkley LC, Cacioppo JT. A meta-analysis of interventions to reduce loneliness. Personality and Social Psychology Review. 2011. https://doi.org/10.1177/1088868310377394
  12. Hickin N, Käll A, Shafran R, et al. The effectiveness of psychological interventions for loneliness: A systematic review and meta-analysis. Clinical Psychology Review. 2021. https://doi.org/10.1016/j.cpr.2021.102066
  13. Hoang P, King JA, Moore S, et al. Interventions Associated With Reduced Loneliness and Social Isolation in Older Adults: A Systematic Review and Meta-analysis. JAMA Network Open. 2022. https://doi.org/10.1001/jamanetworkopen.2022.36676

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