Loneliness and the onset of new mental health problems in the general population: a systematic review

Abstract

Background Loneliness is associated poor health including premature mortality. There are cross sectional associations with depression, anxiety, psychosis and other mental health outcomes. However, the direction of causation is unclear and clarifying the evidence from longitudinal studies is a key step in understanding this relationship. Aims We synthesized evidence from longitudinal studies investigating the relationship between loneliness and new onset of mental health problems, in the general population. Method We systematically searched six electronic databases, unpublished sources and hand-searching of references, up to March 2020. We conducted a meta-analysis of eight independent cohorts, and narrative synthesis of the remaining studies. Results We included 20 studies, of which the majority focused on depression. Our narrative synthesis concluded that loneliness at baseline is associated with subsequent new onset of depression. The few studies on anxiety also showed an association. Our meta analysis found a pooled adjusted odds ratio of 2.33 (95% C.I. 1.62 to 3.34) for risk of new onset depression in adults who were often lonely compared with people who were not often lonely. This should be interpreted with caution given evidence of heterogeneity. Most of the studies were in older adults. Conclusion Loneliness is a public mental health issue. There is growing evidence it is associated with the onset of depression and other common mental health problems. Future studies should explore its impact across the age range, look beyond depression, and explore the mechanisms involved.