Integrating Foundational Theories of Loneliness to Develop Effective Interventions:Running Head: Foundational Theories and Effective Loneliness Interventions

Loneliness is a complex and widespread experience that affects people across all ages and backgrounds. In this paper, we synthesise six foundational theories of loneliness from psychology - Attachment Theory, Social Needs Theory, Cognitive Discrepancy Theory, the Evolutionary Theory of Loneliness, Socio-Ecological Models, and Cultural Theory - to develop a multidimensional approach to intervention. Drawing on reviews of qualitative studies that explore how individuals themselves experience and explain loneliness, we connect theoretical insights to lived realities. That approach enhances the relevance and applicability of existing theories, but it also helps refine them to better reflect individual and cultural variation in both the theories and measurement. By integrating diverse perspectives, we outline practical strategies for prevention and intervention, that address loneliness at the individual, relational, community, and societal levels.