Companion Animals and Loneliness: A Systematic Review of Quantitative Studies

The aim of this systematic review was to evaluate quantitative studies of companion animals and human loneliness. Five electronic databases (PubMed, Medline, Web of Science, Academic Search Premier, Psychlnfo) were searched for articles on companion animals (including animal-assisted therapies [AAT]) and human loneliness. Searches were not limited to a particular language or timeframe. Three randomized controlled studies (RCTs), one controlled study, one prospective cohort study, two longitudinal, and 14 cross-sectional studies satisfied all inclusion criteria and were each evaluated independently by both authors according to standardized criteria, with disagreements resolved by discussion. All except one study was underpowered. The methodological quality of the three RCTs was low, as measured on the Jadad scale. Eleven studies reported positive findings, of which five related to service dogs. While none of the positive studies provided convincing evidence that companion animals help to alleviate loneliness, there was promising evidence that AAT may do this (although effects may be due to aspects of the therapy rather than the animal). As further cross-sectional studies are unlikely to improve understanding of the role of companion animals on human loneliness, we suggest that there is a need for rigorous and adequately powered RCTs.