Close relationships calm your stress system, nudge you towards healthier habits and help you recover from illness. Their effect on lifespan is as large as many physical risk factors, which is why health authorities now call loneliness a public health issue.
Good evidenceUpdated Oct 2026 · 4 new studiesSocial isolation means having few contacts: living alone, rarely seeing people. Loneliness is the painful feeling that your relationships aren't what you need. You can be surrounded by people and still lonely, or alone and content. Both carry health risks.
For most of human history, being cut off from the group was dangerous. Your brain still treats it as a threat: stress hormones rise, sleep gets lighter, blood pressure climbs and the immune system shifts towards inflammation.
Strong relationships do the opposite. They buffer stress, encourage you to see a doctor, eat well and stay active, and give you practical help when you're ill. A sense of purpose (feeling your life has direction and meaning) shows similar protective links.
A few close people you can rely on matter most, but wider circles of friends, neighbours and groups all add support and meaning.
The brain treats isolation as a threat and stays on alert.
More cortisol and adrenaline, lighter sleep, higher blood pressure.
The immune system shifts towards chronic, low-grade inflammation.
Higher risk of heart disease, stroke, dementia, depression and early death.
148 studies, 308,849 people
People with stronger social relationships had 50% higher odds of survival over an average of 7.5 years. The effect was comparable to quitting smoking and bigger than physical inactivity or obesity.
Find on PubMed ↗70 studies, 3.4 million people
Loneliness raised the risk of death by 26%, social isolation by 29% and living alone by 32%.
Find on PubMed ↗23 studies
Poor social relationships were linked to 29% higher risk of heart disease and 32% higher risk of stroke.
Find on PubMed ↗6,985 adults over 50
Those with the lowest sense of purpose had about 2.4 times the death risk of those with the highest.
Find on PubMed ↗276 adults given a cold virus
People with the fewest types of relationships were about 4 times more likely to catch a cold than those with the most varied social lives.
Find on PubMed ↗724 men, then their families
Satisfaction with relationships at age 50 predicted health at 80 better than cholesterol levels did.
Find on PubMed ↗In 2025 the WHO put a global number on loneliness: about 871,000 deaths a year. New work shows how it gets under the skin, through inflammation proteins in the blood, and that a sense of purpose still matters once lifestyle is taken into account. Simple phone-based help can ease loneliness, but the gains are modest.
Every study added to this page since January 2025. Green rings are the strongest evidence: large trials or meta-analyses.
Sutin et al., 2026, 488,765 people followed for up to 32 years. Risk of early death with a strong vs weak sense of purpose, as more factors are accounted for (1 = no difference).
Global evidence review
About 1 in 6 people worldwide feel lonely, and loneliness is linked to around 871,000 deaths a year, roughly 100 every hour. Lonely people are about twice as likely to become depressed.
42,062 UK Biobank adults, 2,920 blood proteins, 14 years
Loneliness and isolation were linked to blood proteins involved in inflammation and immunity. More than half of these proteins predicted heart disease, stroke, type 2 diabetes and death, and five of them partly explained the link between loneliness and those outcomes.
488,765 people in 25 samples, up to 32 years, 48,928 deaths
People with a stronger sense of purpose had about a 24% lower risk of dying early. The link shrank but held after allowing for smoking, weight and blood pressure (15% lower) and for depression (9% lower).
1,151 older adults (average age 77), 12 months
Eight short phone calls from trained volunteers, using either activity planning or mindfulness, lowered loneliness more than friendly chat calls a year later. The effect was real but small, a reminder that there is no quick fix for loneliness.
Treat connection like exercise: schedule it. A regular call, a class, a club or volunteering all count. Purpose matters too, so keep at least one thing in your week that feels meaningful to you.
Treat relationships like exercise: small, regular doses work best.
A call, walk or meal with someone you care about. Put it in the calendar.
A class, club, choir, team, faith group or volunteering. Seeing the same faces builds friendship.
Walking groups, running clubs and cooking with others count twice.
Volunteering is linked to better wellbeing and a stronger sense of purpose.
Brief friendly chats with neighbours or shop staff lift mood more than people expect.
Persistent loneliness, low mood or social anxiety are worth raising with a doctor or counsellor.
✕ MythLoneliness is just an older people's problem.
✓ FactSurveys find young adults report some of the highest rates of loneliness.
✕ MythLots of online friends means I'm connected.
✓ FactOnline contact helps when it leads to real conversations, but it doesn't fully replace in-person time.
✕ MythIntroverts don't need social contact.
✓ FactIntroverts may prefer fewer, deeper relationships, but they benefit from connection too.
There's no magic number. A few close relationships you can rely on matter more than a large network.
Pets can ease loneliness and get you out walking and talking to people, though the research is mixed.
Start with regular activities where you'll see the same people each week. Friendships take time and repetition.
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Strong social relationships are linked to about 50% better odds of survival.
Strong social relationships are linked to about 50% better odds of survival.
Holt-Lunstad 2010 pooled 148 studies and over 300,000 people.
Loneliness is linked to higher risk of heart disease and stroke.
Loneliness is linked to higher risk of heart disease and stroke.
Valtorta 2016 found about 29% higher heart disease risk and 32% higher stroke risk.
Loneliness only affects older people.
Loneliness only affects older people.
Surveys find young adults report some of the highest rates of loneliness.
Being alone is the same as being lonely.
Being alone is the same as being lonely.
Social isolation (few contacts) and loneliness (feeling disconnected) overlap, but you can feel lonely in a crowd or content alone.
Volunteering is linked to better health and longer life.
Volunteering is linked to better health and longer life.
Studies of older volunteers link it to lower death risk and better mood, partly through purpose and connection.
Online contact is worthless for wellbeing.
Online contact is worthless for wellbeing.
Video and voice calls can help, especially when they support in-person ties. Passive scrolling tends not to.
The Harvard Study of Adult Development found relationship quality at 50 predicted health at 80.
The Harvard Study of Adult Development found relationship quality at 50 predicted health at 80.
Satisfaction with relationships was a better predictor than cholesterol levels.
You need lots of friends to be healthy.
You need lots of friends to be healthy.
Quality matters more than quantity. A few close, reliable relationships carry most of the benefit.
Chronic loneliness is linked to higher dementia risk.
Chronic loneliness is linked to higher dementia risk.
Meta-analyses find around 30% higher risk, though some of the link may be early dementia causing withdrawal.
The US Surgeon General declared loneliness a public health epidemic in 2023.
The US Surgeon General declared loneliness a public health epidemic in 2023.
The advisory compared its risk to smoking up to 15 cigarettes a day.
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