Compared with the average person in the study, those who reported being lonely had a 14% greater risk of dying. The figure means that loneliness has around twice the impact on an early death as obesity. Poverty increased the risk of an early death by 19%.

The findings point to a coming crisis as the population ages and people increasingly live alone or far from their families. A study of loneliness in older Britons in 2012 found that more than a fifth felt lonely all the time, and a quarter became more lonely over five years. Half of those who took part in the survey said their loneliness was worse at weekends, and three-quarters suffered more at night.

Previous studies have linked loneliness to a range of health problems, from high blood pressure and a weakened immune system to a greater risk of depression, heart attack and strokes. In his recent book, Loneliness, John Cacioppo, a psychologist at the University of Chicago, says that the pain of loneliness is akin to physical pain.