Chronic loneliness is as damaging to health as smoking 15 cigarettes a day

A meta-analysis by Julianne Holt-Lunstad at Brigham Young University (2015) reviewed 148 studies covering over 300,000 participants and found that social isolation and loneliness increased mortality risk by approximately 26–29% — comparable to smoking 15 cigarettes per day and exceeding the risk from physical inactivity or obesity. The mechanism appears to involve chronic stress hormone elevation, impaired immune function, and disrupted sleep. The UK appointed a Minister for Loneliness in 2018 in response to evidence that loneliness affects approximately 9 million people — more than the number with type 2 diabetes.

Source: Holt-Lunstad et al., Perspectives on Psychological Science (2015)