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 effect the authors placed alongside smoking and physical inactivity. 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 about 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. As the numbers below show, the two do not carry the same risk.

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, the highest of any age band. 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 an estimated 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, and the authors placed the effect alongside smoking, obesity and physical inactivity.

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, poor social relationships were associated with a 29% higher risk of a first coronary event (pooled relative risk 1.29, 95% CI 1.04 to 1.59). Across 8 stroke studies the increase was 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 US National Institute on Aging describes a plausible chain: prolonged loneliness activates the same stress responses as physical pain, sustained stress promotes chronic inflammation and weakens immune defences, and lonely people also tend to move less, sleep worse and smoke more.

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 isolation (32%) to carry more than twice the risk of 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 with between 16 and 90 datasets each, the direction is the same and the size of the effect is consistent. Randomised trials showing that building connection lowers mortality do not yet exist at that scale, which is why the WHO report calls for interventions to be tested rather than assumed.

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 for people who feel lonely 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. Use video calls for family and friends who live far away. 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 social contact and time in 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. And in the regions studied for long life, a strong social fabric is one of the shared features alongside diet and daily movement, 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 hearing has become an obstacle to conversation, get it checked, because untreated hearing loss is a common reason older people withdraw. And if you are under 18 and feel lonely most of the time, tell an adult you trust; the 13 to 29 age band has the highest loneliness rate of all.

A weekly connection plan

Frequently asked

Is loneliness really as harmful as smoking?

The 2010 meta-analysis of 148 studies placed the effect of social relationships on survival in the same range as smoking, obesity and physical inactivity, and the WHO Commission linked loneliness to about 871,000 deaths a year. These are observational comparisons, so they show similar strength of association rather than an identical mechanism.

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 recommends video calls to keep in touch with people who live far away, 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 the highest loneliness rate among 13 to 29 year olds, at 17 to 21%, 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; about 871,000 deaths a year, 100 an hour; depression twice as likely; 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
• 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, 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: Loneliness in older people · Practical advice: groups and classes, being around others, volunteering, video calls, 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

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