People who struggle with social connection — whether they feel lonely, have few relationships or have troubled relationships — face multiple physical and mental health risks, according to a recent advisory from U.S. Surgeon General Murthy. The nation’s “epidemic of loneliness and isolation has been an underappreciated public health crisis,” Murthy said in his announcement about the report, released May 3.

The impact is big, with social disconnection shortening lives by about as much as smoking 15 cigarettes a day, according to the advisory. The causes are complex, with loneliness and isolation affecting everything from inflammation levels in our bodies to the odds that we’ll exercise, eat well or get to a hospital quickly in a crisis. And the problem is widespread: Even before the start of the COVID-19 pandemic, surveys found nearly half of U.S. adults felt lonely.

We’re also spending more time alone and have fewer friends. Half of adults counted three or fewer close friends in 2021, up from a quarter of adults in 1990.

Here are some health risks that people who are chronically lonely or isolated face, according to the report.

1. Premature death

People with strong social bonds live longer and are less likely to die from any cause. One review of 148 studies that followed people for an average of more than seven years found that such bonds increased survival odds by 50 percent. That made social disconnection more dangerous than drinking too much, weighing too much or exercising too little, the advisory said.

2. Heart disease and stroke

Evidence is particularly strong that social disconnection is linked with poor cardiovascular health. People with poor social relationships face a 29 percent increased risk for heart disease and a 32 percent increased risk of stroke, according to data from 16 studies.

A 2022 statement from the American Heart Association (AHA) agreed that social isolation and loneliness can increase the risks of having or dying from heart attacks and strokes. Lonely or isolated people who already have heart disease are more likely to die from it; and those who’ve had one stroke may be at higher risk for another.

3. Diabetes

People with weak social ties are more likely to get diabetes and are less able to manage it well, studies have found. They also are more likely to suffer complications from the disease, such as heart attacks, vision loss, foot problems and kidney damage, regardless of their blood sugar levels.

4. Infections

In one study, people exposed to a cold virus were much less likely to get sick if they had at least six social roles (parent, spouse, friend, family member, coworker or club member), compared with if they had three or fewer roles. A study of COVID-19 vaccination showed weaker immune responses in people who felt disconnected from their neighbors.

5. Cognitive decline and dementia

Adults over age 50 who were followed for an average of six years were about 50 percent more likely to develop dementia if they experienced prolonged loneliness and social isolation, a research review found. Another study that looked at midlife adults found those who were persistently lonely were more likely to later develop Alzheimer’s disease, the most common type of dementia. Additional research has found faster cognitive decline in adults over 65 who report loneliness.

6. Depression and anxiety

It may not be surprising that loneliness and isolation can lead to poor mental health. And the connection goes both ways: Depression and anxiety can cause people to withdraw and feel lonelier. But research also shows that having someone to confide in can sometimes stave off depression, even in people at high risk. Social connection also may lower the risk of suicide, especially for men. 

The link between loneliness and your health

The links between social disconnection and poor health are rooted in our most basic biology, as well as our psychological and behavioral responses, experts say.

We’ve always survived better if we are together.

Multiple biological mechanisms are at work. One that may be particularly important, is chronic inflammation, which is linked to many different diseases and is often elevated in socially isolated people.

Spikes in stress hormones, immune system disturbances and changes in gut microbes also may play roles, the Surgeon General’s advisory says. All that dysregulation can cause a lot of “wear and tear on the body over time.

But loneliness and isolation also change how people behave. For example, having someone around to encourage you to take your medications and go to the doctor when needed may help you manage your health problems. Other people also may help you eat better and move more.

The person who walks half a block on their own might take a much longer walk with a friend or dog. And having a friend or neighbor who checks in on you regularly can literally save your life.