Defining and understanding the next global mental health challenge: chronic loneliness

Background: Loneliness is increasingly recognised by governments, policymakers, and researchers as a critical issue given growing evidence linking it to poorer well-being and adverse mental and physical health. However, developing ways of helping people has been impeded by a lack of clarity as to what is meant by chronic loneliness – a term often used to describe more severe forms of loneliness that contrasts with loneliness, which is experienced by most people and is, in many ways, adaptive.Methods: A systematic review was conducted following the PRISMA guidelines, to answer the question “how is chronic loneliness understood in the literature?”. Texts meeting inclusion criteria were analysed using narrative synthesis by a review team integrating diverse forms of expertise, including lived experience of chronic loneliness, and expertise in loneliness research.Outcomes: 60 papers met the inclusion criteria (combined sample n=191,215). Chronic loneliness is currently understood in multiple ways. It is typically associated with a specific experience that is persistent and enduring, and/or emotionally intense. Yet, quantitative measurements of chronic loneliness tend to focus on the frequency of the experience, sometimes also including measures of stability and duration. Chronic loneliness was hypothesised to arise from interlinked cognitive, dispositional, and social pathways, with certain at-risk subgroups and macro-environmental contexts increasing vulnerability—emphasising the need for tailored interventions to address these complex risks.Interpretation: There is a gap in available quantitative measurements of chronic loneliness that capture chronic loneliness as a qualitatively different, more intense and almost existential form of distress.Funding: The centre for public engagement at QMUL funded the lived experience involvement in this work; JL and PQ received funding from the UKRI (MR/X002381/1).