The shelf · Loneliness and solitude
Does Loneliness hold up?
Loneliness: Human Nature and the Need for Social Connection, by John T. Cacioppo and William Patrick (2008)
A neuroscientist explains loneliness as an evolved signal and describes its effects on body and behaviour.
The short answer
Yes. Both of its main figures stand up, though the share of lonely people depends on how loneliness is measured.
The claims, checked
Roughly 20% of people feel lonely enough for it to be a major source of unhappiness.
Holds with conditions Gallup found 20% of US adults lonely 'a lot of the day yesterday' in 2024. The World Health Organization estimates about 11% in high-income countries.
Evidence: Gallup, 2024
Loneliness is about half genetic and half environmental.
Holds with conditions A study of 8,387 Dutch twins estimated heritability at 48% (Behavior Genetics, 2005). Heritability describes differences across a population, not how much of one person's loneliness comes from genes.
Evidence: Boomsma et al., 2005