Background: Several empirical studies have shown an association between informal caregiving for adults and loneliness or social isolation. Nevertheless, a systematic review is lacking synthesizing studies which have investigated these aforementioned associations. Therefore, our purpose was to give an overview of the existing evidence from observational studies. Materials and Methods: Three electronic databases (Medline, PsycINFO, CINAHL) were searched in June 2021. Observational studies investigating the association between informal caregiving for adults and loneliness or social isolation were included. In contrast, studies examining grandchild care or private care for chronically ill children were excluded. Data extractions covered study design, assessment of informal caregiving, loneliness and social isolation, the characteristics of the sample, the analytical approach and key findings. Study quality was assessed based on the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Each step (study selection, data extraction and evaluation of study quality) was conducted by two reviewers. Results: In sum, twelve studies were included in our review (seven cross-sectional studies and five longitudinal studies)-all included studies were either from North America or Europe. The studies mainly showed an association between providing informal care and higher loneliness levels. The overall study quality was fair to good. Conclusion: Our systematic review mainly identified associations between providing informal care and higher loneliness levels. This is of great importance in assisting informal caregivers in avoiding loneliness, since it is associated with subsequent morbidity and mortality. Moreover, high loneliness levels of informal caregivers may have adverse consequences for informal care recipients.
Keywords: informal caregiving; loneliness; private caregiving; social exclusion; social isolation; spousal caregiving.