What works to reduce loneliness: a rapid systematic review of 101 interventions.

This review evaluates the effectiveness of interventions aimed at reducing loneliness across all age groups. Studies were eligible if alleviation of loneliness was one of ≤ 3 aims, and loneliness was assessed pre- and post-intervention using a validated quantitative measure. Random-effects meta-analyses of standardised mean differences (SMD) assessed pre-post-intervention differences in loneliness, including comparing control and intervention groups. A comprehensive search of peer-reviewed and grey literature sources identified 95 studies covering 101 interventions. Psychological interventions had the largest SMD effect size (n = 23: - 0.79 [95%CI: - 1.19, - 0.38]), followed by social interaction-based interventions (n = 23; - 0.50 [- 0.78, - 0.17]), social support-based interventions (n = 46; - 0.34 [- 0.45, - 0.22]), and finally interventions involving multiple themes (n = 9). Findings highlight the effectiveness of psychological and social interaction strategies in reducing loneliness. Future research should address gaps related to intervention types and populations, emphasising randomised controlled designs. Policymakers and practitioners can use these insights to prioritise interventions fostering social connections and psychological support across diverse settings.