What loneliness does to body and mind

Loneliness is a feeling, but it does not stay only in your head. Over many years, scientists have found that long-lasting loneliness and isolation are linked to real changes in the body. This page explains what they found, what they are less sure about, and why there is real reason for hope.

First, a word about "linked to"

Most of this research follows large groups of people over years. It shows that people who are lonely or isolated are more likely to have certain health problems. That is a link, not proof that loneliness caused the problem.

It can work both ways. Illness can make you lonely (you go out less, you lose your job or your routine), and loneliness can make illness worse. Researchers try to allow for this, but no study can fully separate the two. Keep that in mind as you read.

Also, these are averages over large groups. They do not predict what will happen to you.

Living longer

Two large reviews by psychologist Julianne Holt-Lunstad and colleagues pulled together the results of many studies:

• A 2010 review of 148 studies found that people with stronger social relationships had about a 50%Higher likelihood of survival for people with stronger social relationships (Holt-Lunstad et al., 2010; 148 studies)As of July 27, 2010.148 studies, 308,849 people, followed for 7.5 years on average.Source: Holt-Lunstad, Smith & Layton, Social Relationships and Mortality Risk: A Meta-analytic Review, PLOS Medicine (2010) higher likelihood of survival over the study period.
• A 2015 review found that, after allowing for other factors, loneliness was linked to a 26%Higher likelihood of early death linked to loneliness (Holt-Lunstad et al., 2015; 70 studies)As of March 11, 2015.After allowing for other factors. A link, not proof of cause.Source: Holt-Lunstad et al., Loneliness and Social Isolation as Risk Factors for Mortality, Perspectives on Psychological Science (2015) higher likelihood of early death, social isolation to 29%Higher likelihood of early death linked to social isolation (Holt-Lunstad et al., 2015)As of March 11, 2015.Source: Holt-Lunstad et al., Loneliness and Social Isolation as Risk Factors for Mortality, Perspectives on Psychological Science (2015), and living alone to 32%Higher likelihood of early death linked to living alone (Holt-Lunstad et al., 2015)As of March 11, 2015.Source: Holt-Lunstad et al., Loneliness and Social Isolation as Risk Factors for Mortality, Perspectives on Psychological Science (2015).

The U.S. Surgeon General's 2023 advisory said that the risk of early death from lacking social connection is comparable to smoking 15 cigarettes a daySmoking level whose early-death risk is comparable to lacking social connection (Surgeon General, 2023)As of May 3, 2023.Source: U.S. Surgeon General: Our Epidemic of Loneliness and Isolation (2023). The comparison is meant to show how seriously to take it, not to say the two work the same way.

Heart and stroke

The Surgeon General's advisory reported that poor social relationships are linked to a 29%Higher risk of heart disease linked to poor social relationships (Surgeon General, 2023)As of May 3, 2023.Source: U.S. Surgeon General: Our Epidemic of Loneliness and Isolation (2023) higher risk of heart disease and a 32%Higher risk of stroke linked to poor social relationships (Surgeon General, 2023)As of May 3, 2023.Source: U.S. Surgeon General: Our Epidemic of Loneliness and Isolation (2023) higher risk of stroke. Research also links long-lasting loneliness to higher blood pressure in middle-aged and older adults.

Memory and dementia

• The Surgeon General's advisory linked loneliness and isolation in older adults to about a 50%Higher risk of developing dementia for older adults linked to loneliness and isolation (Surgeon General, 2023)As of May 3, 2023.Source: U.S. Surgeon General: Our Epidemic of Loneliness and Isolation (2023) higher risk of developing dementia.
• The 2024 Lancet Commission on dementia, a large international expert group, lists social isolation in later life as one of 14 risk factors that people and societies can change. It estimates that about 45%Share of future dementia that could in theory be prevented or delayed if 14 risk factors, including social isolation, were removed (Lancet Commission, 2024)As of July 31, 2024.All 14 factors together, not social isolation alone.Source: Alzheimer Europe: 2024 Lancet Commission identifies 14 modifiable risk factors of future dementia could in theory be prevented or delayed if all 14 were removed. (That figure is for all 14 together, not for isolation alone.)

Researchers are still working out why. Ideas include that talking with people keeps the brain active, that isolation goes along with less movement and more stress, and that early memory changes can themselves cause people to withdraw. Hearing loss, also on the Lancet list, often leads to isolation, which is one reason a hearing test can matter.

Mood: depression and anxiety

• WHO reports that people who feel lonely are about twice as likelyHow much more likely people who feel lonely are to become depressed (WHO, 2025)As of June 30, 2025.Source: WHO: Social connection linked to improved health and reduced risk of early death (30 June 2025) to become depressed.
• Loneliness is also linked to anxiety, and to thoughts of self-harm or suicide.
• It works in both directions: depression can make you pull away from people, which can deepen loneliness.

If you feel low most days, read Depression and loneliness. If social situations make you very anxious, read Social anxiety and shyness.

Sleep

Research suggests loneliness affects how well you sleep more than how long. People who feel lonely tend to report more broken sleep and more tiredness the next day. One idea is that when we feel alone, part of the brain stays a little more "on guard" at night. Tips are on Sleep, food and movement.

Stress, immune system and inflammation

Studies by John Cacioppo, Louise Hawkley and others found that long-lasting loneliness is linked to:

• higher levels of stress hormones,
• signs of more inflammation in the body (inflammation is linked to many long-term diseases),
• weaker responses in some parts of the immune system, including in one study a weaker response to a flu vaccine.

These studies are smaller and still developing, but they point in the same direction.

Other links

WHO's 2025 report also links loneliness and isolation to diabetes, to lower grades for teenagers (teens who felt lonely were 22%Higher likelihood of lower grades or qualifications for teenagers who felt lonely (WHO, 2025)As of June 30, 2025.Source: WHO: Social connection linked to improved health and reduced risk of early death (30 June 2025) more likely to get lower grades or qualifications), and to harder times finding or keeping work.

The hopeful part

This is the most important section on the page.

• Connection is protective. Social connection is now treated by health agencies as a health factor in its own right. The same research that shows the risks shows the benefits: people with good relationships tend to live longer and healthier lives.
• Loneliness can change. It is a feeling, not a fixed trait. People become less lonely at every age, often through small, steady steps.
• Small things count. Research does not say you need a big circle of friends. A few people you can count on, regular friendly contact, and a sense of belonging all help.
• Looking after your body helps your mood too. Sleep, movement, time outdoors and hearing or vision checks all make connecting easier.

Where to go next

• The loneliness trap: why loneliness can make itself worse, and how to break the cycle.
• Small first steps
• Getting help: therapy, free and low-cost options