The complex science of tailoring loneliness interventions

Loneliness requires urgent action, both as public health and as social justice issue. However, existing loneliness interventions have shown limited effectiveness, likely due, in part, to the assumption that ‘one-size-fits-all' approaches guide intervention attempts. Drawing on methodologically and disciplinarily pluralistic principles, we propose new directions for designing, implementing, and evaluating tailored interventions. These new directions are necessary to prevent or reduce loneliness considering its complexity. We first problematise state of the art loneliness interventions, focusing on issues of definition, one-size-fits-all approaches, theoretical frameworks, and evaluation, and framing these as challenges for the field. We then introduce four ‘complexity dimensions’ of loneliness, i.e., transdisciplinarity, multilevel aetiology, conceptual diversity, and temporal dynamics, which can help us to understand the how, whom, what, and when of effective interventions. Further, we present a diverse set of methods related to participatory research, precision health and complex systems illustrated with case studies that can be used to address the complexity dimensions of loneliness within interventions. This perspective has implications for designing and evaluating future loneliness interventions, including the need to consider the multilevel interventional context, to frame loneliness interventions within theoretical frameworks, and to explore how this approach may be applied to issues beyond loneliness.