Loneliness
The felt gap between the contact a person wants and the contact they have. Living alone and a thin network are different measures.
Surveys ask whether someone feels left out, isolated, or lacking companionship. That score can rise in a busy house and stay low in a one-person flat. Social capital on this atlas is network density. Depression is a mood disorder on a named scale. Loneliness is the feeling.
Also called felt loneliness, perceived isolation, UCLA loneliness.
Connected relationships
Observational · Low
Loneliness→Depression
Higher Loneliness increases Depression.
Hysing 2026 followed 10,460 Norwegian university students: those in the highest fifth of a 2022 Three-Item Loneliness Scale score, against the lowest fifth, had more CIDI major depressive episodes a year later (relative risk 2.02 in women and 2.64 in men after age and baseline Hopkins symptoms).
Meta-analysis · Low
Loneliness→All-cause mortality
Higher Loneliness increases All-cause mortality.
Wang 2023 pooled 90 prospective cohorts in 2,205,199 adults and found loneliness associated with a 14 percent higher all-cause death risk (effect size 1.14, 1.08 to 1.20). Nobody randomized loneliness.
Sources
- M Hysing et al. (2026). From loneliness to depression: A longitudinal diagnostic study among Norwegian university students.
- F Wang et al. (2023). A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality.
- A Nakou et al. (2025). Loneliness, social isolation, and living alone: a comprehensive systematic review, meta-analysis, and meta-regression of mortality risks in older adults.
- B Yu et al. (2022). Social isolation, loneliness, and all-cause mortality: A cohort study of 35,254 Chinese older adults.
- SL Kraav et al. (2021). The effects of loneliness and social isolation on all-cause, injury, cancer, and CVD mortality in a cohort of middle-aged Finnish men. A prospective study.