Is loneliness bad for your health? What the studies show

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The short answer

In large studies that followed people for years, those who were lonely or socially isolated were more likely to die during the study years, and more likely to develop heart disease, stroke and type 2 diabetes, than people with strong social ties. The differences are modest, and they come from observational studies, which show a link rather than proof of cause. Genetic studies, which can test cause more directly, disagree on whether loneliness itself does the harm or mostly travels with other risks. Some programs reduce loneliness by a small to moderate amount in trials. As of the American Heart Association's 2022 review, no trial had tested whether easing loneliness prevents heart disease or extends life. Connection is still worth treating as a long-term habit, alongside sleep, exercise and food. In one trial, easing loneliness also eased depression and anxiety.

Lonely and isolated are two different things

Social isolation means having few people around you: living alone, rarely seeing friends or family, or having a small circle. Loneliness is the feeling that your connections fall short of what you want. You can be surrounded by people and still feel lonely, or live alone and feel fine. Researchers measure both, and both show up in the health data.

What the long-term studies found

A widely cited analysis pooled 148 studies of about 309,000 people, mostly in North America and Europe, followed for an average of seven and a half years. People with stronger social relationships had about 50 percent higher odds of still being alive at the end of follow-up than people with weaker ones. That analysis grouped every kind of social measure together, from marriage to the size of a person's network. It also mostly used each study's figure before adjustment for other factors, such as age and health.

A 2023 analysis of 90 studies and 2.2 million adults looked at the two measures separately. Social isolation was linked with a 32 percent higher risk of death from any cause, and loneliness with a 14 percent higher risk. These are relative figures. They do not tell us how many extra deaths there were per 1,000 people.

Heart disease, blood pressure and blood sugar

A review of long-term studies in high-income countries, which followed people for 3 to 21 years, found that people with poor social relationships had a 29 percent higher risk of coronary heart disease and a 32 percent higher risk of stroke. Coronary heart disease is narrowing of the heart's arteries, the condition that leads to most heart attacks.

Blood pressure may be one pathway. In a study of 229 adults aged 50 to 68 in Chicago, people who were lonelier at the start had larger rises in systolic blood pressure, the top number, over the next four years. For two people whose loneliness scores differed by a typical amount, one standard deviation, the lonelier person was predicted to have about 2.3 points more rise. It is a small study, and the result points to a possible pathway rather than a settled one.

Type 2 diabetes shows a similar pattern. Among 4,112 adults in England with an average age of 65, about 6 in 100 developed type 2 diabetes over about 10 to 12 years. Each one-point step up on a three-point loneliness scale, roughly the difference between hardly ever and sometimes feeling lonely, was linked with a 46 percent higher risk. That held after accounting for age, wealth, smoking, physical activity, alcohol, body weight, blood sugar and high blood pressure, and the authors described the link as small. A 2025 analysis of nine studies and 1.1 million people found loneliness linked with a 32 percent higher risk of type 2 diabetes, and social isolation with a smaller and less certain 20 percent higher risk.

Where the cigarette comparison comes from

You may have heard that loneliness is as harmful as smoking 15 cigarettes a day. The 2023 US Surgeon General's advisory on loneliness made a version of that comparison. It said that lacking social connection can raise the risk of early death as much as smoking up to 15 cigarettes a day. The comparison comes from charts that set the size of the social-connection finding beside the size of a smoking finding from a separate analysis of different people. No study measured the two head to head, and the advisory labels its own chart a visual approximation. It is a way to convey scale, and it should be read that way.

What we don't know yet

In 2022 the American Heart Association reviewed this research. It concluded that isolation and loneliness appear to be independent risk factors for worse heart and brain health, most consistently for death from heart disease and stroke. It also noted that the effects are small and that factors the studies did not measure may explain part of the link. No study had yet tested whether reducing isolation or loneliness improves heart or brain outcomes.

Genetic studies raise a second question. They use inherited differences in people's genes as a kind of natural experiment. A 2024 analysis of the UK Biobank, a large study of British adults followed for about 12 years, found loneliness linked with many diseases, but social and economic circumstances, health habits, depression and other illnesses largely explained those links. Its genetic analysis did not support loneliness as a cause of heart and blood vessel disease, type 2 diabetes or chronic kidney disease. A 2023 genetic study pointed the other way for type 2 diabetes and suggested a small causal effect. Loneliness may be partly a cause and partly a marker of other risks, and the research has not settled how much is which.

What helps with loneliness

Several kinds of programs have been tested in randomized trials, where people are assigned to groups by chance. In Texas, researchers studied 240 adults who received home-delivered meals. Most were 65 or older, and more than half lived alone. They were assigned either to receive phone calls from young callers aged 17 to 23, trained in empathetic conversation, or to receive no calls. The calls came daily for the first five days and at least twice a week after that. After four weeks, scores on the main loneliness questionnaire, which runs from 3 to 9, had improved by about 1 point compared with no calls. Depression and anxiety scores also improved.

A 2021 review of 28 trials with about 3,000 people found that psychological approaches reduced loneliness by a small to moderate amount. The most common was cognitive behavioral therapy, a structured talking therapy that works on unhelpful thoughts and habits. An earlier review of 20 randomized trials found that the four programs that helped people change how they think about social situations did better than programs that offered more social support or taught social skills.

What you can do

Put contact on your calendar. In the Texas trial, people who received regular, scheduled calls from a friendly caller felt less lonely within four weeks.
Notice the thoughts that keep you from reaching out. Programs that worked on how people think about social situations did best in an earlier review of trials.
If loneliness comes with low mood that does not lift, talk to your doctor. Talking therapies reduced loneliness by a small to moderate amount in trials.
Count connection as part of your health plan, alongside sleep, exercise and food, and give it regular time the way you would a walk.

References

Holt-Lunstad J, Smith TB, Layton JB. PLoS Med. 2010;7(7):e1000316. https://doi.org/10.1371/journal.pmed.1000316
Across 148 studies of 308,849 people followed for an average of 7.5 years, stronger social relationships were linked with 50 percent higher odds of survival. Its Figure 6 places this result beside a smoking estimate from a separate analysis. Observational, meta-analysis.
Wang F, et al. Nat Hum Behav. 2023;7(8):1307-1319. https://doi.org/10.1038/s41562-023-01617-6
In 90 cohort studies of 2.2 million adults, social isolation was linked with a 32 percent and loneliness with a 14 percent higher risk of death from any cause. Observational, meta-analysis.
Valtorta NK, et al. Heart. 2016;102(13):1009-1016. https://doi.org/10.1136/heartjnl-2015-308790
Across long-term studies in high-income countries, poor social relationships were linked with a 29 percent higher risk of coronary heart disease and a 32 percent higher risk of stroke. Observational, meta-analysis.
Hawkley LC, et al. Psychol Aging. 2010;25(1):132-141. https://doi.org/10.1037/a0017805
In 229 Chicago adults aged 50 to 68, greater loneliness predicted larger rises in systolic blood pressure over four years. Observational.
Hackett RA, Hudson JL, Chilcot J. Diabetologia. 2020;63(11):2329-2338. https://doi.org/10.1007/s00125-020-05258-6
Among 4,112 adults in England, each one-point rise on a 1-to-3 loneliness score was linked with a 46 percent higher risk of type 2 diabetes after adjustment for lifestyle and health factors. Observational.
Ezzatvar Y, et al. Diabetes Res Clin Pract. 2025;223:112124. https://doi.org/10.1016/j.diabres.2025.112124
Across 9 cohort studies and 1.1 million people, loneliness was linked with a 32 percent and social isolation with a 20 percent higher risk of type 2 diabetes. Observational, meta-analysis.
Office of the Surgeon General. Our Epidemic of Loneliness and Isolation: The U.S. Surgeon General's Advisory on the Healing Effects of Social Connection and Community. Washington, DC: US Department of Health and Human Services; 2023. https://www.hhs.gov/sites/default/files/surgeon-general-social-connection-advisory.pdf
Compares the effect of lacking social connection on early death with smoking up to 15 cigarettes a day, using a chart it describes as a visual approximation. Government report.
Cené CW, et al. J Am Heart Assoc. 2022;11(16):e026493. https://doi.org/10.1161/JAHA.122.026493
Concludes that isolation and loneliness appear to be independent risk factors for worse heart and brain health, notes that the effect estimates are small, and found no intervention studies on heart or brain outcomes. Scientific statement.
Liang YY, et al. Nat Hum Behav. 2024;8(11):2209-2221. https://doi.org/10.1038/s41562-024-01970-0
In UK Biobank adults followed for a median of 12.2 years, loneliness was linked with most disease categories, but socioeconomic factors, health habits, depression and other illnesses largely explained the links, and genetic analysis did not support a causal role for most diseases, including cardiovascular disease, type 2 diabetes and chronic kidney disease. Observational and Mendelian randomization.
Song Y, et al. EClinicalMedicine. 2023;64:102236. https://doi.org/10.1016/j.eclinm.2023.102236
In 423,503 UK Biobank and 13,800 Chinese adults, loneliness was linked with about 21 percent higher risk of type 2 diabetes, and genetic analysis suggested a small possible causal effect. Observational and Mendelian randomization.
Kahlon MK, et al. JAMA Psychiatry. 2021;78(6):616-622. https://doi.org/10.1001/jamapsychiatry.2021.0113
In 240 adults receiving home-delivered meals in Texas, four weeks of empathy-focused phone calls lowered loneliness, depression and anxiety scores compared with no calls. Randomized trial.
Hickin N, et al. Clin Psychol Rev. 2021;88:102066. https://doi.org/10.1016/j.cpr.2021.102066
Across 28 randomized trials with about 3,000 people, psychological interventions, most often cognitive behavioral therapy, reduced loneliness by a small to moderate amount. Randomized trials, meta-analysis.
Masi CM, et al. Pers Soc Psychol Rev. 2011;15(3):219-266. https://doi.org/10.1177/1088868310377394
Among 20 randomized studies, the four programs that addressed unhelpful thinking about social situations reduced loneliness more than programs that added social support or taught social skills. Randomized trials, meta-analysis.

One study explained in plain language every week, with sources attached: https://www.selfprinciple.org/newsletter

This content is for educational purposes only and is not medical advice. Always consult your healthcare provider for individual care. The views expressed are Dr. Sean Hashmi's own and do not represent his employer.