Is loneliness really as bad as smoking 15 cigarettes a day?

You have seen the line: loneliness is as bad for you as smoking 15 cigarettes a day. It has appeared in news stories, a US Surgeon General advisory and countless wellness posts. It is a striking comparison, and it is worth knowing what it was actually measuring.

Where the 15 cigarettes comes from

The comparison traces to a 2010 PLoS Medicine meta-analysis by Julianne Holt-Lunstad and colleagues. It pooled 148 studies and 308,849 people and found that those with stronger social relationships had 50% greater odds of survival over an average follow-up of 7.5 years. That figure is about social relationships in general, from marriage to friendships to group involvement. Complex measures of social integration showed the biggest effect, and living alone was not statistically significant on its own. Only 8 of the 148 studies measured loneliness.

The paper's text never says 15 cigarettes. The comparison lives in a chart, where one bar is labeled "Smoking < 15 cigarettes daily." By 2017 Holt-Lunstad was writing that lacking social connection carries a risk comparable to, and in many cases exceeding, smoking up to 15 cigarettes a day. The US Surgeon General's 2023 advisory repeated the comparison, in wording Utah State University Extension quotes: the mortality impact of being socially disconnected is similar to that caused by smoking up to 15 cigarettes a day.

What later evidence says about loneliness itself

Later analyses pulled loneliness apart from isolation and found a smaller effect than the headline implies. A 2015 meta-analysis found loneliness linked to a 26% higher likelihood of death and social isolation to 29%, in studies that controlled for confounders. A 2023 analysis in Nature Human Behaviour pooled 90 cohorts and 2,205,199 people and found loneliness linked to a 14% higher risk of death from any cause and social isolation to a 32% higher risk. Those are real associations. They are not what most people picture when they hear "as bad as smoking."

Why the smoking comparison is shaky

In 2024, Tyler VanderWeele of Harvard and Eric Kim of the University of British Columbia wrote in the American Journal of Epidemiology that it was unclear how the smoking estimate in the 2010 figure was derived. They noted that the smoking category the chart drew on, generally 10 to 20 cigarettes a day, carries a relative risk of about 2.0, higher than the figure showed. A 2023 paper co-written by Holt-Lunstad herself said the smoking analogy often oversimplifies the evidence.

Does loneliness cause the harm?

Even where the link is real, cause is hard to prove. Holt-Lunstad's 2010 paper says causality is not easily established, because you cannot randomly assign people to be isolated. A 2024 UK Biobank analysis followed participants for a median of 12.2 years. Loneliness was linked to 30 of 56 diseases, but genetic analyses found non-causal associations for 20 of 26 diseases tested, including cardiovascular disease, type 2 diabetes and obesity. Its authors suggested loneliness may be a marker rather than a cause for most of them. The World Health Organization is more confident, calling the mortality links probably causal, and says the connections between loneliness and physical, cognitive and mental health run in both directions. Dementia shows why: a 2022 analysis of 16 cohorts linked loneliness to 23% higher dementia risk, but loneliness may also be an early sign of the disease.

And the death toll

WHO estimates loneliness is linked to about 100 deaths every hour, more than 871,000 a year. That number is modeled, not counted. The report applies a single pooled risk estimate of 1.14, from the 2023 analysis, across all ages and regions, leaving out children under 13.

What to do about it

Take loneliness seriously as a health signal without treating it as a precise cigarette equivalent. WHO suggests reaching out to a friend in need, putting your phone away to be fully present in conversation, greeting a neighbor, joining a local group or volunteering. The evidence that interventions help is real but thin: a review of 28 randomized trials with 3,039 people found psychological interventions reduced loneliness, while another review found most had a small effect and rated the overall evidence very low quality. We found no trial showing that reducing loneliness in healthy people extends life. For how stress and isolation can compound, see our piece on how chronic stress affects your life, and talk to a clinician if loneliness is persistent.

Our take

Loneliness and weak social ties are linked to earlier death, and that deserves attention. But the 15 cigarettes line is a rhetorical shortcut: it came from social relationships in general, the smoking figure has been questioned by researchers in the field, and loneliness itself shows a smaller link. Staying connected is worth doing because it makes life better, not because of a cigarette count.

This is general information, not medical advice. Talk to a clinician before changing anything, especially if you are pregnant, nursing, or managing a condition.