1. Berguno G, Leroux P, McAinsh K, Shaikh S. Children's experience of loneliness at school and its relation to bullying and the quality of teacher interventions. Qualitative Report. 2004; 9: 483–499.

2. Pinquart M, Sorensen S. Influences on loneliness in older adults: A meta-analysis. Basic and Applied Social Psychology. 2001; 23: 245–266.

3. Weeks DJ. A review of loneliness concepts, with particular reference to old age. International Journal of Geriatric Psychiatry. 1994; 9: 345–355.

4. Peplau L, Perlman D. Perspectives on loneliness. In: Peplau L, Perlman D, eds. Loneliness: A sourcebook of current theory, research, and therapy. New York: Wiley; 1982.

5. Hawkley LC, Hughes ME, Waite LJ, et al. From social structure factors to perceptions of relationship quality and loneliness: The Chicago Health, Aging, and Social Relations Study. Journal of Gerontology: Social Sciences. 2008; 63B: S375–S384.

6. Wheeler L, Reis H, Nezlek J. Loneliness, social interaction, and sex roles. J Pers Soc Psychol. 1983; 45: 943–953.

7. Russell D, Peplau LA, Cutrona CE. The revised UCLA Loneliness Scale: Concurrent and discriminant validity evidence. J Pers Soc Psychol. 1980; 39: 472–480.

8. Cacioppo JT, Hawkley LC, Ernst JM, et al. Loneliness within a nomological net: An evolutionary perspective. Journal of Research in Personality. 2006; 40: 1054–1085.

9. Cacioppo JT, Hawkley LC. Perceived social isolation and cognition. Trends in Cognitive Sciences. 2009; 13: 447–454.

10. Heinrich LM, Gullone E. The clinical significance of loneliness: A literature review. Clin Psychol Rev. 2006; 26: 695–718.

11. Theeke LA. Predictors of loneliness in U.S. adults over age sixty-five. Arch Psychiatr Nurs. 2009; 23: 387–396.

12. Caspi A, Harrington H, Moffitt TE, Milne BJ, Poulton R. Socially isolated children 20 years later: Risk of cardiovascular disease. Arch Pediatr Adolesc Med. 2006; 160: 805–811.

13. Eaker ED, Pinsky J, Castelli WP. Myocardial infarction and coronary death among women: Psychosocial predictors from a 20-year follow-up of women in the Framingham Study. Am J Epidemiol. 1992; 135: 854–864.

14. Olsen RB, Olsen J, Gunner-Svensson F, Waldstrøm B. Social networks and longevity. A 14 year follow-up study among elderly in Denmark. Soc Sci Med. 1991; 33: 1189–1195.

15. Penninx BW, van Tilburg T, Kriegsman DM, et al. Effects of social support and personal coping resources on mortality in older age: The Longitudinal Aging Study Amsterdam. Am J Epidemiol. 1997; 146: 510–519.

16. Seeman T. Health promoting effetcs of friends and family on health outcomes in older adults. American Journal of Health Promotion. 2000; 14: 362–370.

17. Shiovitz-Ezra S, Ayalon L. Situational versus chronic loneliness as risk factors for all-cause mortality. Int Psychogeriatr. 2010; 22: 455–462.

18. Sugisawa H, Liang J, Liu X. Social networks, social support, and mortality among older people in Japan. J Gerontol. 1994; 49: S3–13.

19. Thurston RC, Kubzansky LD. Women, loneliness, and incident coronary heart disease. Psychosom Med. 2009; 71: 836–842.

20. Hawkley LC, Cacioppo JT. Aging and loneliness: Downhill quickly? Current Directions in Psychological Science. 2007; 16: 187–191.

21. Hawkley LC, Masi CM, Berry JD, Cacioppo JT. Loneliness is a unique predictor of age-related differences in systolic blood pressure. Psychol Aging. 2006; 21: 152–164.

22. Hawkley LC, Thisted RA, Masi CM, Cacioppo JT. Loneliness predicts increased blood pressure: Five-year cross-lagged analyses in middle-aged and older adults. Psychol Aging. 2010; 25: 132–141.

23. DeNiro DA. Perceived alienation in individuals with residual-type schizophrenia. Issues Ment Health Nurs. 1995; 16: 185–200.

24. Neeleman J, Power MJ. Social support and depression in three groups of psychiatric patients and a group of medical controls. Soc Psychiatry Psychiatr Epidemiol. 1994; 29: 46–51.

25. Richman NE, Sokolove RL. The experience of aloneness, object representation, and evocative memory in borderline and neurotic patients. Psychoanalytic Psychology. 1992; 9: 77–91.

26. Goldsmith SK, Pellmar TC, Kleinman AM, Bunney WE. Reducing Suicide: A National Imperative. Washington, DC: National Academy Press; 2002.

27. Gow AJ, Pattie A, Whiteman MC, Whalley LJ, Deary IJ. Social support and successful aging: Investigating the relationships between lifetime cognitive change and life satisfaction. Journal of Individual Differences. 2007; 28: 103–115.

28. Tilvis RS, Kahonen-Vare MH, Jolkkonen J, et al. Predictors of cognitive decline and mortality of aged people over a 10-year period. J Gerontol (A Biol Sci Med Sci). 2004; 59: M268–M274.

29. Wilson RS, Krueger KR, Arnold SE, et al. Loneliness and risk of Alzheimer disease. Arch Gen Psychiatry. 2007; 64: 234–240.

30. Cacioppo JT, Ernst JM, Burleson MH, et al. Lonely traits and concomitant physiological processes: The MacArthur social neuroscience studies. Int J Psychophysiol. 2000; 35: 143–154.

31. Hawkley LC, Thisted RA, Cacioppo JT. Loneliness predicts reduced physical activity: Cross-sectional and longitudinal analyses. Health Psychol. 2009; 28: 354–363.

32. Cacioppo JT, Hughes ME, Waite LJ, Hawkley LC, Thisted RA. Loneliness as a specific risk factor for depressive symptoms: Cross-sectional and longitudinal analyses. Psychology and Aging. 2006; 21: 140–151.

33. Segrin C. Social skills, stressful events, and the development of psychosocial problems. Journal of Social & Clinical Psychology. 1999; 18: 14–34.

34. Heikkinen R-L, Kauppinen M. Depressive symptoms in late life: A 10-year follow-up. Arch Gerontol Geriat. 2004; 38: 239–250.

35. Wei M, Russell DW, Zakalik RA. Adult Attachment, Social Self-Efficacy, Self-Disclosure, Loneliness, and Subsequent Depression for Freshman College Students: A Longitudinal Study. Journal of Counseling Psychology. 2005; 52: 602–614.

36. Cacioppo JT, Hawkley LC, Thisted RA. Perceived social isolation makes me sad: Five year cross-lagged analysis of loneliness and depressive symptomatology in the Chicago Health, Aging, and Social Relations study. Psychol Aging. 2010; 25: 453–463.

37. Newall N, Chipperfield J, Clifton R, et al. Causal beliefs, social participation, and loneliness among older adults: A longitudinal study. Journal of Social and Personal Relationships. 2009; 26: 273–290.

38. Tice DM, Bratslavsky E. Giving in to feel good: The place of emotion regulation in the context of general self-control. Psychological Inquiry. 2000; 11: 149–159.

39. McAuley E, Morris KS, Motl RW, et al. Long-term follow-up of physical activity behavior in older adults. Health Psychol. 2007; 26: 375–380.

40. Penedo FJ, Dahn JR. Exercise and well-being: A review of mental and physical health benefits associated with physical activity. Curr Opin Psychiatr. 2005; 18: 189–193.

41. Lauder W, Mummery K, Jones M, Caperchione C. A comparison of health behaviours in lonely and non-lonely populations. Psychology, Health, and Medicine. 2006; 11: 233–245.

42. Akerlind I, Hornquist JO. Loneliness and alcohol abuse: A review of evidences of an interplay. Soc Sci Med. 1992; 34: 405–414.

43. Stranahan AM, Khalil D, Gould E. Social isolation delays the positive effects of running on adult neurogenesis. Nature Neurosci. 2006; 9: 526–533.

44. Mullington JM, Haack M, Toth M, Serrador JM, Meier-Ewert HK. Cardiovascular, inflammatory, and metabolic consequences of sleep deprivation. Prog Cardiovasc Dis. 2009; 51: 294.

45. Gangwisch JE, Heymsfield SB, Boden-Albala B, et al. Short sleep duration as a risk factor for hypertension: Analyses of the first national health and nutrition examination survey. Hypertension. 2006; 47: 833–839.

46. King CR, Knutson KL, Rathouz PJ, et al. Short sleep duration and incident coronary artery calcification. JAMA. 2008; 300: 2859–2866.

47. Kripke DF, Garfinkel L, Wingard DL, Klauber MR, Marler MR. Mortality associated with sleep duration and insomnia. Arch Gen Psychiatry. 2002; 59: 131–136.

48. Ohayon MM. Prevalence and correlates of nonrestorative sleep complaints. Arch Intern Med. 2005; 165: 35–41.

49. Cacioppo JT, Hawkley LC, Crawford LE, et al. Loneliness and health: Potential mechanisms. Psychosom Med. 2002; 64: 407–417.

50. Friedman EM, Hayney MS, Love GD, et al. Social relationships, sleep quality, and interleukin-6 in aging women. PNAS. 2005; 102: 18757–18762.

51. Jacobs JM, Cohen A, Hammerman-Rozenberg R, Stessman J. Global sleep satisfaction of older people: The Jerusalem Cohort Study. J Am Geriatr Soc. 2006; 54: 325–329.

52. Mahon NE. Loneliness and sleep during adolescence. Perceptual & Motor Skills. 1994; 78: 227–231.

53. Cacioppo JT, Hawkley LC, Berntson GG, et al. Do lonely days invade the nights? Potential social modulation of sleep efficiency. Psychol Sci. 2002; 13: 385–388.

54. Akerstedt T, Hume K, Minors D, Waterhouse J. The meaning of good sleep: A longtitudinal study of polysomnography and subjective sleep quality. J Sleep Res. 2009; 3: 152–158.

55. Hawkley LC, Preacher KJ, Cacioppo JT. Loneliness impairs daytime functioning but not sleep duration. Health Psychol. 2010; 29: 124–129.

56. Hawkley LC, Burleson MH, Berntson GG, Cacioppo JT. Loneliness in everyday life: Cardiovascular activity, psychosocial context, and health behaviors. J Pers Soc Psychol. 2003; 85: 105–120.

57. Franklin SS, Gustin WI, Wong ND, et al. Hemodynamic patterns of age-related changes in blood pressure: The framingham heart study. Circulation. 1997; 96: 308–315.

58. Schiffrin EL. Vascular stiffening and arterial compliance: Implications for systolic blood pressure. Am J Hypertens. 2004; 17: S39–S48.

59. Cheitlin MD. Cardiovascular physiology-changes with aging. The American Journal of Geriatric Cardiology. 2003; 12: 9–13.

60. Folkow B, Svanborg A. Physiology of cardiovascular aging. Physiol Rev. 1993; 73: 725–764.

61. Toro L, Marijic J, Nishimaru K, et al. Aging, ion channel expression, and vascular function. Vascular Pharmacology. 2002; 38: 73–80.

62. Danesh J, Wheeler JG, Hirschfield GM, et al. C-reactive protein and other circulating markers of inflammation in the prediction of coronary heart disease. N Engl J Med. 2004; 350: 1387–1397.

63. Yusuf S. Effect of potentially modifiable risk factors associated with myocardial infarction in 52 countries (the INTERHEART study). Lancet. 2004; 364: 937–952.

64. Beevers G, Lip GY, O'Brien E. ABC of hypertension: The pathophysiology of hypertension. Br Med J (Clinical research ed). 2001; 322: 912–916.

65. Black HR, Bakris GL, Elliott WJ. Hypertension: epidemiology, pathophysiology, diagnosis, and treatment. In: Fuster V, Alexander RW, O’Rourke RA, eds. Hurst's the Heart. 10th ed. New York: McGraw-Hill; 2001:1553-604.

66. Guyenet PG. The sympathetic control of blood pressure. Nature Rev Neurosci. 2006; 7: 335–346.

67. Girod JP, Brotman DJ. Does altered glucocorticoid homeostasis increase cardiovascular risk? Cardiovasc Res. 2004; 64: 217–226.

68. Nijm J, Jonasson L. Inflammation and cortisol response in coronary artery disease. Ann Med. 2009; 41: 224–233.

69. Whitworth JA, Schyvens CG, Zhang Y, Mangos GJ, Kelly JJ. Glucocorticoid-induced hypertension: From mouse to man. Clin Exp Pharmacol Physiol. 2001; 28: 993–996.

70. Kiecolt-Glaser JK, Ricker D, George J, et al. Urinary cortisol levels, cellular immunocompetency, and loneliness in psychiatric inpatients. Psychosom Med. 1984; 46: 15–23.

71. Steptoe A, Owen N, Kunz-Ebrecht SR, Brydon L. Loneliness and neuroendocrine, cardiovascular, and inflammatory stress responses in middle-aged men and women. Psychoneuroendocrinology. 2004; 29: 593–611.

72. Pressman SD, Cohen S, Miller GE, et al. Loneliness, social network size, and immune response to influenza vaccination in college freshmen. Health Psychol. 2005; 24: 297–306.

73. Adam EK, Hawkley LC, Kudielka BM, Cacioppo JT. Day-to-day dynamics of experience-cortisol associations in a population-based sample of older adults. Proc Nat Acad Sci USA. 2006; 103: 17058–17063.

74. Dickerson SS, Kemeny ME. Acute stressors and cortisol responses: A theoretical integration and synthesis of laboratory research. Psychol Bull. 2004; 130: 355–391.

75. Cole SW, Hawkley LC, Arevalo JM, et al. Social regulation of gene expression in human leukocytes. Genome Biology. 2007; 8: R189.181–R189.113.

76. Cole SW. Social regulation of leukocyte homeostasis: The role of glucocorticoid sensitivity. Brain Behav Immun. 2008; 22: 1049–1055.

77. Levine S, Mody T. The long-term psychobiological consequences of intermittent postnatal separation in the squirrel monkey. Neurosci Biobehav Rev. 2003; 27: 83–89.

78. Pan Y, Liu Y, Young KA, Zhang Z, Wang Z. Post-weaning social isolation alters anxiety-related behavior and neurochemical gene expression in the brain of male prairie voles. Neurosci Lett. 2009; 454: 67–71.

79. Poletto R, Steibel JP, Siegford JM, Zanella AJ. Effects of early weaning and social isolation on the expression of glucocorticoid and mineralocorticoid receptor and 11beta-hydroxysteroid dehydrogenase 1 and 2 mRNAs in the frontal cortex and hippocampus of piglets. Brain Res. 2006; 1067: 36–42.

80. Dixon D, Cruess S, Kilbourn K, et al. Social Support Mediates Loneliness and Human Herpesvirus Type 6 (HHV-6) Antibody Titers. Journal of Applied Social Psychology. 2001; 31: 1111–1132.

81. Glaser R, Kiecolt-Glaser JK, Speicher CE, Holliday JE. Stress, loneliness, and changes in herpesvirus latency. J Behav Med. 1985; 8: 249–260.

82. Kiecolt-Glaser JK, Garner W, Speicher C, et al. Psychosocial modifiers of immunocompetence in medical students. Psychosom Med. 1984; 46: 7–14.

83. Straits-Troster KA, Patterson TL, Semple SJ, et al. The relationship between loneliness, interpersonal competence, and immunologic status in HIV-infected men. Psychology and Health. 1994; 9: 205–219.

84. Miller GE, Kemeny ME, Taylor SE, Cole SW, Visscher BR. Social relationships and immune processes in HIV seropositive gay and bisexual men. Ann Behav Med. 1997; 19: 139–151.

85. Cattan M, White M. Developing evidence based health promotion for older people: A systematic review and survey of health promotion interventions targeting social isolation and loneliness among older people. Internet Journal of Health Promotion. 1998; 13: 1–9.

86. Cattan M, White M, Bond J, Learmouth A. Preventing social isolation and loneliness among older people: A systematic review of health promotion interventions. Aging & Society. 2005; 25: 41–67.

87. Findlay R: Interventions to reduce social isolation amongst older people: Where is the evidence? Abstracts in Social Gerontology. 2004; 47.

88. McWhirter BT. Loneliness: A Review of Current Literature, with Implications for Counseling and Research. Journal of Counseling and Development. 1990; 68: 417–422.

89. Perese E, Wolf M. Combating loneliness among persons with severe mental illness: Social network interventions' characteristics, effectiveness, and applicability. Issues in Mental Health Nursing. 2005; 26: 591–609.

90. Rook KS. Promoting social bonding: Strategies for helping the lonely and socially isolated. Am Psychol. 1984; 39: 1389–1407.

91. Lipsey MW, Wilson DB. Practical Meta-Analysis. Thousand Oaks: Sage; 2001.

92. Cacioppo JT, Patrick B. Loneliness: Human Nature and the Need for Social Connection. New York: Norton; 2008.

93. Routasalo PE, Tilvis RS, Kautiainen H, Pitkala KH. Effects of psychosocial group rehabilitation on social functioning, loneliness and well-being of lonely, older people: Randomized controlled trial. J Adv Nurs. 2009; 65: 297–305.

94. Pitkala KH, Routasalo P, Kautiainen H, Tilvis RS. Effects of psychosocial group rehabilitation on health, use of health care services, and mortality of older persons suffering from loneliness: A randomized, controlled trial. J Gerontol (A Biol Sci Med Sci). 2009; 64: 792–800.

95. Wilson DS. Evolution for Everyone: How Darwin's Theory Can Change the Way We Think About Our Lives. New York: Delacorte; 2007.

96. Cacioppo JT, Amaral DG, Blanchard JJ, et al. Social neuroscience: Progress and implications for mental health. Perspectives on Psychological Science. 2007; 2: 99–123.

97. Donaldson ZR, Young LJ. Oxytocin, vasopressin, and the neurogenetics of sociality. Science. 2008; 322: 900–904.

98. Lovejoy CO. Reexamining human origins in light of Ardipithecus ramidus. Science. 2009; 326: 74e71–74e78.

99. Emler N. Gossip, reputation, and adaptation. In: Goodman R, Ben Ze'ev A, eds. Good Gossip. Lawrence: University of Kansas Press; 1994: 34–46.