Suicidal thoughts and behaviors and social isolation: A narrative review of the literature

Background
Social isolation is one of the main risk factors associated with suicidal outcomes. The aim of this narrative review was to provide an overview on the link between social isolation and suicidal thoughts and behaviors.
Methods
We used the PubMed database to identify relevant articles published until April 13, 2018. We focused on: (a) systematic reviews, meta-analyses, and narrative reviews; (b) original observational studies with large samples (N ≥ 500); and (c) qualitative studies. We included all relevant suicidal outcomes: suicidal ideation (SI), suicidal planning, non-suicidal self-injury, deliberate self-harm, suicide attempt (SA), and suicide.
Results
The main social constructs associated with suicidal outcomes were marital status (being single, separated, divorced, or widowed) and living alone, social isolation, loneliness, alienation, and belongingness. We included 40 original observational studies, the majority of them performed on adolescents and/or young adults (k = 23, 57.5%). Both the objective condition (e.g., living alone) and the subjective feeling of being alone (i.e., loneliness) were strongly associated with suicidal outcomes, in particular with SA and SI. However, loneliness, which was investigated in most studies (k = 24, 60%), had a major impact on both SI and SA. These associations were transculturally consistent.
Limitations
Confounding factors can limit the weight of the results obtained in observational studies.
Conclusions
Data from the observational studies suggest that both objective social isolation and the subjective feeling of loneliness should be incorporated in the risk assessment of suicide. Interventional studies targeting social isolation for suicide prevention are needed.