How loneliness affects health

Loneliness is more than a sad feeling. Large studies now link it, and being cut off from other people, to heart disease, stroke, dementia, depression and an earlier death.^1,2 In 2023, the U.S. Surgeon General issued a national advisory about it. In 2025, a World Health Organization (WHO) commission called it a major global health concern.^1,3

This page explains what the research shows, what it does not show, and why the numbers matter for you. The good news is that connection is something you can build at any age. Our page on ways to feel more connected has ideas.

Loneliness and isolation are not the same

Researchers look at two related things:^1,2

• Loneliness is a painful feeling. It comes when the relationships you have do not match the ones you want or need. You can feel lonely in a crowd or in a marriage.
• Social isolation means having few relationships or seeing people rarely. It can be counted. A person can be isolated and not feel lonely.

Both matter for health, and they often go together. In the research below, we say which one a study measured when it makes a difference.

How common is it?

Loneliness is common, and surveys find different numbers depending on how they ask.

• In the U.S., about 1 in 3 adults say they feel lonely, and about 1 in 4 say they lack social and emotional support.⁴ The Surgeon General's 2023 advisory reported that about half of U.S. adults had felt lonely.¹
• Around the world, about 1 in 6 people are affected by loneliness.^2,3
• Up to 1 in 3 older adults worldwide are socially isolated.² In the U.S., about 1 in 4 people aged 65 and older who live in the community are socially isolated.¹²

Later life brings losses that can shrink a person's circle, such as retirement, the death of a spouse, hearing loss or giving up driving. Read more in loneliness in later life.

Loneliness and length of life

The strongest finding is about how long people live.

A large 2010 review pooled 148 studies with about 309,000 people, followed for an average of 7.5 years. People with stronger social ties had about 50% better odds of being alive at the end of the studies.⁵ The authors said the size of this effect was similar to well-known risks such as smoking.⁵

A 2015 review looked at each part separately. After accounting for other health factors, it found a higher risk of dying early with:⁶

The Surgeon General's advisory said that lacking social connection may raise the risk of early death about as much as smoking up to 15 cigarettes a day.¹ This is a comparison of risk sizes from different studies, not a head-to-head test. Still, it shows that social ties belong on the list of things that affect health.

WHO estimates that loneliness is linked to about 871,000 deaths a year worldwide. That is about 100 deaths every hour.³

Heart disease and stroke

A 2016 review pooled 23 papers from 16 long-term studies. Poor social relationships, meaning loneliness, isolation or both, were linked to:⁷

• About a 29% higher risk of heart disease (a heart attack, chest pain from narrowed arteries, or death from heart disease)
• About a 32% higher risk of stroke

In 2022, the American Heart Association reviewed the research and reached a similar conclusion. It also found that people who already have heart disease or have had a stroke do worse when they are isolated or lonely. They have a higher risk of another stroke and of death.⁸

Heart failure. Among people with heart failure (when the heart does not pump as well as it should), those who felt very lonely had about a 68% higher risk of a hospital stay and a 57% higher risk of an emergency room visit.¹

Other body conditions. Research also links weak social ties to type 2 diabetes and high blood pressure.^1,2,4 Lonely people and people with little support may also get sicker after being exposed to cold and flu viruses.¹

Memory, thinking and dementia

Many families ask whether loneliness can affect the brain. The research says it is linked.

A 2024 analysis combined 21 groups of people, more than 608,000 people in all. People who felt lonely had:⁹

The Surgeon General's advisory put the dementia risk for older adults with long-term loneliness and isolation at about 50% higher. It also linked them to faster decline in thinking skills.¹

In 2024, a major expert group called the Lancet Commission listed social isolation as one of 14 risk factors for dementia that people can change. The commission estimated that close to half of dementia cases (45%) might be prevented or delayed if all 14 were removed.¹¹ Hearing loss is another of the 14. It often goes hand in hand with isolation. See hearing loss, loneliness and the brain.

Because these studies watch people over time, they cannot fully show which comes first. Either way, a person who is becoming withdrawn is worth checking on. Our page on staying mentally and socially active covers what you can do.

Depression, anxiety and suicide

Loneliness and low mood feed each other.

• Adults who often feel lonely have more than twice the odds of developing depression compared with those who rarely or never do.¹ WHO reached the same conclusion: lonely people are about twice as likely to become depressed.²
• A study in England followed 4,211 adults aged 50 and older for 12 years. Loneliness predicted more depression symptoms years later. This held even after the researchers accounted for social isolation, support and genes.¹⁰
• The same study estimated that between about 1 in 10 and 1 in 6 cases of depression (11% to 18%) might be avoided if loneliness were removed.¹⁰
• The link runs both ways. Isolated people are more likely to become depressed, and depressed people are more likely to pull away from others.⁸

Loneliness and isolation are also linked to anxiety and to thoughts of suicide or self-harm.^2,4 The Surgeon General's report named social isolation as one of the strongest predictors of suicidal thoughts.¹ Feeling lonely is not a sign of weakness. It is a signal that a basic need is not being met, and help works.

Learn more about depression, depression in later life and anxiety.

Why might loneliness harm the body?

Researchers think several paths work together:^1,8

• Stress. Without people to lean on, problems can feel heavier. Long-term stress keeps the body on alert, which strains the heart and blood vessels. See what stress does to the body.
• Inflammation. Isolation and low support are linked to higher levels of inflammation (the body's swelling and defense response). Long-lasting inflammation plays a part in many chronic diseases.¹
• Daily habits. Lonely or isolated people tend to move less, eat fewer fruits and vegetables, and are more likely to smoke.⁸ Friends and family also affect sleep, diet and whether people take their medicines.¹
• Less help in a crisis. People who live with others or have more contact are less likely to die from a heart attack. One reason may be that help comes faster.¹
• Mood. Depression, which loneliness can help trigger, is itself one of the 14 changeable risk factors for dementia.¹¹

What the numbers mean and do not mean

Most of these studies are observational. That means researchers watched what happened to people over time. They did not assign some people to be lonely. So the studies show strong links, but they cannot prove that loneliness alone causes disease.⁷

Two other points help keep the numbers in perspective:

• Higher risk is not certainty. A "30% higher risk" compares groups of people. It does not mean a lonely person has a 30% chance of getting sick. Many lonely people stay well, and many connected people do get sick.
• The findings are steady. The links show up across many countries, many studies and many years. They remain after researchers account for age, health and other factors.^5,6 That is why the Surgeon General, WHO and the American Heart Association all treat social connection as a real health issue.^1,3,8

The hopeful side is that social connection is a risk factor you can change. In 2025, WHO reported that some approaches, such as talking therapies like CBT (cognitive behavioral therapy), skills training, group activities and doctors referring people to community programs, can help.² Our page on ways to feel more connected walks through options.

Small steps that count

You do not need a big social life to gain from connection. The Surgeon General suggested simple daily actions:¹

• Answer the phone when friends call, and reach out first sometimes.
• Share a meal with someone.
• Put your phone away and listen fully when you talk with someone.
• Do something kind or helpful for another person.

If you are caring for someone who is withdrawing, see helping someone who is isolated. If you are a caregiver feeling cut off yourself, see caregiver burnout.

When to get help

Talk with your doctor if loneliness has lasted for weeks, or if you notice:

• Low mood, loss of interest, or trouble sleeping most days
• Pulling away from people and activities you used to enjoy
• New memory or thinking problems
• Trouble hearing in conversations

Experts have urged doctors to ask about isolation, especially after big life changes like a move or the death of a spouse.¹² You can bring it up yourself. It is a fair health question, just like blood pressure.

Education only. This page is general information written from the sources listed. It is not medical, legal or financial advice and does not replace a doctor, therapist or lawyer who knows your situation. How we write and check pages.