Life

Social connection and health: what the large studies show

The people around you are a measurable health factor. In a meta-analysis of 148 studies with 308,849 participants, people with stronger social relationships had 50% higher odds of survival over an average follow-up of 7.5 years, an association the authors themselves illustrated by setting it beside smoking. A 2023 review of 90 cohort studies and 2,205,199 adults linked social isolation to a 32% higher risk of death from any cause and loneliness to 14%, and in 2025 the WHO Commission on Social Connection estimated that loneliness is linked to more than 871,000 deaths a year, roughly 100 an hour.

Loneliness and isolation are two different measurements

Researchers count two different things. Social isolation is objective: how many people you live with, see, speak to and can call on. Loneliness is subjective: the distressing feeling that the contact you have is less than you want. The two overlap but do not match. You can live alone, see a handful of people a week and feel fine, and you can feel lonely in a full house.

The scale of the problem was put into figures by the WHO Commission on Social Connection, set up in 2023, in its report of 30 June 2025. About 1 in 6 people worldwide is affected by loneliness. Among 13 to 29 year olds, 17 to 21% reported feeling lonely, with the highest rates among teenagers. In low-income countries about 24% of people reported loneliness, twice the roughly 11% in high-income countries. Social isolation, the objective measure, affects up to 1 in 3 older adults and 1 in 4 adolescents. The commission linked loneliness to more than 871,000 deaths a year, around 100 every hour, and to stroke, heart disease, diabetes, cognitive decline and depression.

What the mortality studies found

The study most often quoted is a meta-analysis by Holt-Lunstad and colleagues, published in PLoS Medicine in 2010. It pooled 148 prospective studies with 308,849 participants, followed for an average of 7.5 years. The average age at the start was 63.9 years, and over the follow-up an average of 29% of the participants in each study died. People with stronger social relationships had 50% higher odds of being alive at the end of follow-up (odds ratio 1.50, 95% confidence interval 1.42 to 1.59). The finding held across age, sex, initial health status and cause of death. To show how large that is, the authors set it beside other risk factors: comparable with smoking, larger than obesity and physical inactivity. That comparison is their own illustration of effect size, not a claim of a shared mechanism.

How social ties were measured mattered a great deal. Complex measures of social integration, which combine several questions about roles, network size and contact, showed the strongest association (odds ratio 1.91). The weakest was the simplest, a yes or no answer to living alone (odds ratio 1.19, with a confidence interval of 0.99 to 1.44 that just crosses 1). The number of people under your roof predicts little; the breadth and quality of your contacts predict more.

A larger and more recent review, published in Nature Human Behaviour in 2023 by Wang and colleagues, pooled 90 prospective cohort studies with 2,205,199 adults aged 18 or older. In the general population, social isolation was associated with a 32% higher risk of death from any cause (pooled effect 1.32, 95% CI 1.26 to 1.39) and loneliness with a 14% higher risk (1.14, 1.08 to 1.20). Social isolation was also linked to a 34% higher risk of cardiovascular death and a 24% higher risk of cancer death; for loneliness the cancer figure was 9%, with a confidence interval of 1.01 to 1.17 that only just reached significance. In people who already had cardiovascular disease, isolation went with a 28% higher risk of death, and in women with breast cancer with 51%.

Heart, stroke and mood

Death is a blunt endpoint, so a team at the University of York looked at new disease instead. Their 2016 review in the journal Heart screened 35,925 records and kept 23 papers reporting on 16 longitudinal datasets from high-income countries, with 4,628 coronary heart disease events and 3,002 strokes recorded over follow-up periods of 3 to 21 years. Across the 11 studies with usable coronary data, covering 3,794 of those events, people who scored high on loneliness or isolation had a 29% higher risk of a first coronary event than people who scored low (pooled relative risk 1.29, 95% CI 1.04 to 1.59). Across the 8 stroke studies the same comparison gave 32% (1.32, 1.04 to 1.68). Men and women did not differ.

Mental health shows the same direction. The WHO commission reported that people who are lonely are twice as likely to become depressed, and that loneliness is also linked to anxiety and to thoughts of self-harm. The effect reaches beyond health: teenagers who felt lonely were 22% more likely to get lower grades or qualifications. The mechanisms are still being worked out. The York authors list three plausible routes: health behaviours, since physical inactivity and smoking are more common in lonely and isolated people; psychology, since loneliness goes with lower self-esteem and less active coping; and physiology, since it is associated with impaired immune function and higher blood pressure. The WHO adds that social connection can reduce inflammation.

What the evidence cannot tell you

Every figure above comes from observational cohorts, so it shows association, not proof of cause. The York authors say so plainly: they could not infer causality, rule out confounding, or exclude reverse causation. Reverse causation is the largest question mark: illness pushes people out of social life, so some of the excess deaths among isolated people belong to disease that was already present. The 2010 meta-analysis found its result held regardless of initial health status, which argues against reverse causation explaining the whole effect, but cannot remove it.

Two further cautions. First, who was studied. The average participant in the 2010 analysis was 63.9 years old, and 7 of the estimates in the Heart meta-analysis came from samples that were wealthier and healthier than the general population; the York authors also warn that publication bias may inflate the pooled effect. Second, the measures. Loneliness is self-reported and isolation is counted by questionnaire, and both are snapshots taken at the start of follow-up. That the 2023 review found the excess risk with isolation (32%) to be more than twice the excess with loneliness (14%) may reflect real biology, or simply that an objective count is easier to measure reliably than a feeling.

What the evidence does support is modest and useful: across three reviews pooling 16, 90 and 148 datasets, the direction is the same and the effect sizes fall in a similar range. Randomised trials showing that building connection lowers mortality do not yet exist at that scale, which is why research and better measurement, including a global social connection index, are two of the five areas in the WHO roadmap.

Building connection week by week

None of the studies prescribe a dose, but the 2010 analysis points to what to build: several kinds of contact rather than one, and regular roles rather than occasional company. The NHS advice is practical. Join a group or class built around something you enjoy. Spend time in places where you are simply around other people, such as a park, a cinema or a cafe. Volunteer with a charity or organisation near you. Keep in touch with friends and family by phone or video call. Consider peer support, where people with similar experiences help each other. Activities with a fixed weekly slot are the easiest to keep; our guide on how long a habit takes to form explains why the first 2 to 3 months decide whether it sticks.

Shared outdoor activity gives you contact and green surroundings in one go: a walking group, an allotment or a community garden, which we cover in gardening as exercise and therapy and green space and mental health. A strong social fabric is also one of the shared features of the regions studied for long life, as set out in what the longest-lived regions have in common.

See a doctor in a few situations. The NHS advises seeing your GP if you have had a low mood for more than 2 weeks, if you are struggling to cope with stress, anxiety or low mood, or if the things you have tried yourself are not helping; ask about social prescribing, through which a link worker connects you to local groups and activities. If you need help urgently, call your local urgent care or emergency number (in the UK, NHS 111 or 999); if you are having thoughts of harming yourself, treat that as an emergency and get help the same day. The WHO links loneliness and isolation to stroke, heart disease, diabetes and cognitive decline, so it is worth mentioning at your next appointment. And if you are under 18 and feel lonely most of the time, tell an adult you trust; the WHO reports the highest loneliness rates among teenagers.

A weekly connection plan

Frequently asked

Is loneliness really as harmful as smoking?

No. That comparison comes from the 2010 meta-analysis of 148 studies, where the authors illustrated the size of their result by setting it beside other risk factors: comparable with smoking, and larger than obesity or physical inactivity. It compares the strength of two observational associations, not the mechanism, and the two are not the same kind of exposure.

What is the difference between loneliness and social isolation?

Social isolation is an objective count of contacts and household members; loneliness is the feeling that you have less contact than you want. You can be one without the other. In the 2023 review of 2.2 million adults, isolation carried a 32% higher risk of death and loneliness 14%.

Does living alone put me at risk?

Not by itself. In the 2010 meta-analysis, living alone was the weakest of all measures (odds ratio 1.19, with a confidence interval that crossed 1), while broad measures of social integration were the strongest (1.91). What matters is how many roles and contacts you have, not who shares your address.

Do phone and video calls count as social connection?

The NHS suggests keeping in touch with friends and family by phone or video call, and they are a good bridge. The large studies mostly measured contact frequency, group membership and household ties, so the evidence for remote contact on its own is thinner than for meeting people in person.

Are young people affected, or is this an older adults' problem?

Both. The WHO reported that 17 to 21% of 13 to 29 year olds felt lonely, with the highest rates among teenagers, and up to 1 in 4 adolescents socially isolated, alongside up to 1 in 3 older adults. Lonely teenagers were 22% more likely to get lower grades or qualifications.

When should I see a doctor about loneliness?

The NHS advises seeing your GP if you have had a low mood for more than 2 weeks, are struggling to cope, or self-help is not working. Ask about social prescribing, and if you need help urgently, use your local urgent care or emergency number.

Sources

• WHO, 30 June 2025: Social connection linked to improved health and reduced risk of early death (report of the WHO Commission on Social Connection) · 1 in 6 people affected by loneliness; 17 to 21% of 13 to 29 year olds; 24% in low-income versus 11% in high-income countries; up to 1 in 3 older adults and 1 in 4 adolescents isolated; more than 871,000 deaths a year, 100 an hour; depression twice as likely; loneliness linked to anxiety and thoughts of self-harm; teenagers 22% more likely to get lower grades
• Holt-Lunstad et al. 2010, PLoS Medicine: Social relationships and mortality risk, a meta-analytic review · 148 studies, 308,849 participants, average follow-up 7.5 years, average age 63.9, 49% women; OR 1.50 for survival; complex social integration OR 1.91; living alone OR 1.19 (0.99 to 1.44); 29% of participants died during follow-up; authors call the effect comparable with smoking and larger than obesity and physical inactivity
• Wang et al. 2023, Nature Human Behaviour: A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality · 90 prospective cohorts, 2,205,199 adults aged 18 and over; social isolation 1.32 all-cause, 1.34 cardiovascular, 1.24 cancer mortality; loneliness 1.14 all-cause, 1.09 cancer; 1.28 in people with cardiovascular disease, 1.51 in breast cancer; abstract open, full text behind a paywall
• Valtorta et al. 2016, Heart: Loneliness and social isolation as risk factors for coronary heart disease and stroke, systematic review and meta-analysis of longitudinal observational studies · 16 databases searched, 35,925 records, 23 papers, 16 datasets, 4,628 coronary and 3,002 stroke events, follow-up 3 to 21 years; RR 1.29 for coronary heart disease (11 studies) and 1.32 for stroke (8 studies); authors note no causal inference, possible publication bias, 7 estimates from healthier samples
• NHS: Feeling lonely, what to try and when to get medical help · Advice for adults of any age, with a section on older people: groups and classes, being around others, volunteering, phone and video contact, peer support, social prescribing via a GP link worker; see a GP if low mood lasts more than 2 weeks or self-help is not working; NHS 111 for urgent help and 999 in an emergency

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This guide is for general information. It does not replace medical advice or an examination.