Carmen Chai

Allison Young, MD

on March 14, 2024

Feeling isolated, left out, and without a sense of belonging or connection to anyone around you — in other words, grappling with loneliness — can be a grim experience.

Science suggests these pangs for companionship aren’t just uncomfortable. Chronic loneliness can have significant effects on our physical and mental health.

“What’s so powerful about loneliness is it affects everything — every aspect of health and well-being,” says Angelina Sutin, PhD, a professor of psychology at Florida State University College of Medicine in Tallahassee, who researches how personality and life events affect mental and physical outcomes. “This underscores the importance of social connection and being able to be part of a group.”

Loneliness is the emotional and cognitive discomfort or uneasiness of being or perceiving oneself to be alone — the distress we feel when our inherent needs for intimacy and connection aren’t met.

It can bubble up as either an objective or subjective state. You could be objectively alone and crave companionship, or you could be in a crowded room and still feel alone in the world, says Julianne Holt-Lunstad, PhD, professor of psychology and neuroscience at Brigham Young University in Provo, Utah. For the past two decades, she’s been studying the protective effects of social relationships on health — and, in turn, the health risks associated with loneliness and isolation.

Limiting social interaction for months and years, for some, because of a global pandemic has been a stark reminder of the toll loneliness can take. In February 2021, Harvard University research reported that 36 percent of Americans said they felt “serious loneliness.”

Another international study (for which Dr. Holt-Lunstad was a coauthor) included 101 countries and suggested approximately 21 percent of people experienced “severe” loneliness in 2020 (only 6 percent reported that level of loneliness before COVID-19).

The increasing number of people experiencing loneliness led to the release of a U.S. Surgeon General’s Advisory in 2023, calling attention to loneliness as an urgent public health issue.

While nearly everyone experiences loneliness at some point, it’s chronic loneliness that wreaks havoc on our health. Here’s a look at seven ways loneliness affects our health and well-being.

1. Loneliness May Lead to Poor Health Habits

Evidence suggests people who feel lonelier may engage in more unhealthy behaviors compared with people who feel more socially connected.

Research suggests single or widowed seniors eat fewer vegetables and fruits than their peers who are married or cohabitating.

Other research found that people who are lonely were significantly less likely to exercise than people who felt less lonely.

Factors like marital status, contact with close social ties, and social network size did not explain why people were more or less likely to exercise, but reported feelings of loneliness did.

One report found that loneliness led people to poor health behaviors. Forty-three percent of people who felt loneliness turned to binge eating, 34 percent smoked cigarettes, and 21 percent abused alcohol or drugs to soothe their feelings.

These lifestyle factors play a key role in people’s health trajectories, Holt-Lunstad says. Her ongoing research on the COVID-19 pandemic is attempting to better understand how loneliness stemming from lockdowns and social distancing worsened our health overall.

“When people are isolated and lonely, they tend to eat more, they don’t work out, they get worse sleep. Their health-related behaviors become worse,” she says.

2. Loneliness May Interfere With Sleep

Loneliness has been linked to insufficient sleep among older adults.

Loneliness has also been linked to fragmented sleep, or more disrupted sleep.

Researchers have suggested that we need to feel secure in our surroundings for a genuinely restful night’s sleep.

3. Loneliness May Increase Risk of Depression

Loneliness is a major risk factor for developing depression, with many symptoms overlapping (like experiencing feelings of emotional pain and helplessness).

In a study published in January 2021 in The Lancet Psychiatry, researchers concluded that loneliness increases the risk of depression.

The researchers had a group of more than 4,200 adults in England answer questions about their experiences of loneliness, social support, and symptoms of depression.

Each 1-point increase on the 20-point loneliness scale used was linked to a 0.16-point increase in depressive symptoms. Depression also increased over time among participants with greater loneliness scores, hinting that present day loneliness may be a marker for future depression.

4. Loneliness May Trigger Chronic Inflammation

Inflammation is part of how our immune systems kick into action to protect us against harm or disease, or heal.

Chronic inflammation is this process gone awry. The body continues to send distress signals even though there’s no injury or danger. This type of chronic inflammation causes chronic health problems, like heart disease, type 2 diabetes, rheumatoid arthritis, and cancer.

In a meta-analysis, researchers concluded that people who are more socially isolated have higher levels of inflammatory chemicals that are associated with poor health.

That finding suggests that our bodies interpret loneliness as stress, injury, or pain.

5. Chronic Loneliness Increases Dementia Risk

Adults who report greater feelings of loneliness are at a 40 percent increased risk of developing dementia and other cognitive impairments, according to a study led by Dr. Sutin that was published in 2018.

The research analyzed data from a U.S. longitudinal study of more than 12,000 people, making it the largest sample to date to look at loneliness and dementia. Study participants were 50 and older. They completed surveys to measure loneliness and completed cognitive tests every two years over the course of a decade.

Sutin says that people who were lonely had risk factors for diabetes, hypertension, depression, and other concerns, but even after adjusting for those shared risks, loneliness still predicted increased risk of dementia.

Making conversation and nurturing relationships with coworkers, loved ones, neighbors, and others is great for our cognitive health, Sutin says. “There’s something about connecting with other people, having a reason to get up in the morning to engage with the world that protects the brain. It’s about keeping the brain active and on its toes,” she says.

Other research aligns, suggesting that feeling lonely, not social isolation, is what increases dementia risk.

And another study among Chinese adults suggests that the risk is higher for men.

6. Data Finds Loneliness Is Bad for Your Heart

Loneliness has been tied to a 29 percent increased risk of heart disease and a 32 percent increased risk of having a stroke, according to a meta-analysis.

Previous research has also suggested that people age 45 and older who live alone have a 27 percent increased risk of dying of heart disease.

Previous research has also suggested that loneliness increases blood pressure.

7. Loneliness May Shorten Your Life

Ultimately, loneliness takes a grave toll on our health, with research suggesting that both living alone and feeling subjective loneliness increases risk of premature death by 32 and 26 percent. These findings stem from a meta-analysis that involved over 3.4 million participants, which was led by Holt-Lunstad.

Potential confounding factors were controlled for.

“When we’re alone or away from a group we, in essence, have to deal with everything by ourselves and our brains are much more vigilant. It’s like being in a constant heightened state of alert similar to a fight or flight mode,” Holt-Lunstad says.

On the flipside, Holt-Lunstad’s research found that strong social connection is linked to a 50 percent reduced risk of an early death.

In this case, researchers followed the health trajectories of more than 308,000 people over the course of seven and a half years. They found that scoring low on indicators of social connection was a greater risk to health than air pollution, obesity, smoking, and excessive drinking.

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