Not surprisingly loneliness and mental health are related. The question has been which comes first: does loneliness cause poor mental health, or does poor mental health cause loneliness? Recent research has shown that loneliness is a much better predictor of psychological distress a year later than vice versa (Saeri et al 2018). This suggests that loneliness is typically a precursor of mental health issues.
Loneliness is related to social anxiety, depression, paranoia, dementia, and obsessive-compulsive symptoms.
Loneliness has been found to be a mediator from anxiety to depression (Ebesutani et al 2015). Loneliness is a predictor of subsequent social anxiety, while social anxiety is also a predictor of loneliness. This suggests “that loneliness may be a potential antecedent to emerging mental health symptoms and that identifying and treating co-occurring social anxiety symptoms may reduce the severity of loneliness.” (Lim et al 2016).
Loneliness has been found to be a predictor of subsequent changes in depressive symptoms, but not vice versa (Cacioppo et al 2010). For example, loneliness at ages 5 and 9 is a predictor of depressive symptoms at age 13 (Qualter et al 2010); loneliness at the beginning of a college semester is a predictor of depression later in the semester (Rich et al 1987); and loneliness in elderly is a predictor of depression three years later (Green et al 1992).
Loneliness is a predictor of subsequent paranoia (Lim et al 2016). Consistent with the paranoia finding, depression has been found to be mediator from loneliness to paranoia (Jaya et al 2017).
All these findings imply causal links:
Social anxiety ↔ loneliness → depression → paranoia
For the elderly, feelings of loneliness but not social isolation predict the onset of clinical dementia (Holwerda 2014).
High levels of obsessive-compulsive symptoms have been associated with greater perceived loneliness, especially for females (Timpano et al 2014).
Alexander Saeri, Tegan Cruwys, Fiona Barlow, and Chris Sibley (2018), “Social connectedness improves public mental health: Investigating bidirectional relationships in the New Zealand attitudes and values survey”, Australian & New Zealand journal of psychiatry, vol. 52(4), p. 365-374. Read the abstract.
John Cacioppo, Louise Hawkley, and Ronald Thisted (2010), “Perceived social isolation makes me sad: 5-Year cross-lagged analyses of loneliness and depressive symptomatology in the Chicago health, aging, and social relations study”, Psychology and aging, vol. 25(2), p. 453–463. Read the article.
Pamela Qualter, Stephen Brown, Penny Munn and Ken Rotenburg (2010), “Childhood loneliness as a predictor of adolescent depressive symptoms: an 8-year longitudinal study”, European child & adolescent psychiatry, vol. 19, p. 493–501.
Alexander Rich & Martha Scovel (1987), “Causes of depression in college students: A cross-lagged panel correlational analysis”, Psychological reports, vol. 60, p. 27−30. Read the abstract.
B. Green, J. Copeland, M. Dewey, V. Sharma, P. Saunders, L. Davidson, et al. (1992), “Risk factors for depression in elderly
people: A prospective study”, Acta psychiatrica Scandinavica, vol. 86, p. 213−217. Read the abstract.
Chad Ebesutani, Matthew Fierstein, Andres Viana, Lindsay Trent, John Young & Manuel Sprung (2015), “The role of loneliness in the relationship between anxiety and depression in clinical and school-based youth”, Psychology in the schools, vol. 52(3), p. 223-234. Read the article.
Michelle Lim, Thomas Rodebaugh, Michael Zypher, and John Gleeson (2016), “Loneliness over time: The crucial role of social anxiety”, Journal of abnormal psychology, vol. 125(5), p. 620–630. Read the abstract.
Edo Jaya, Tobias Hillmann, Klaus Reininger, Anton Gollwitzer, and Tania Lincoln (2017), “Loneliness and psychotic symptoms: The mediating role of depression”, Cognitive therapy and research, vol. 41, p. 106–116. Read the article.
Tjalling Holwerda, Dorly Deeg, Aartjan Beekman, Theo Tilburg, Max Stek, Cees Jonker, and Robert Schoevers (2014), “Feelings of loneliness, but not social isolation, predict dementia onset: results from the Amsterdam Study of the Elderly (AMSTEL)”, Journal of Neurology, Neurosurgery and psychiatry, vol. 85, p. 135–142. Read the abstract.
Kiara Timpano, Demet Çek, Liza Rubenstein, Dennis Murphy, and Norman Schmidt (2014), “Exploring the association between obsessive-compulsive symptoms and loneliness: Consideration of specificity and gender”, Journal of cognitive psychotherapy, vol. 28(4), p. 264-273. Read the abstract.