Table 3.

Actionable insights and recommendations for the consideration of policymakers

Category	Recommendation	Implications
Language	Use accessible language in policy documents and briefs	To ensure that ideas and concepts can be traced back to the scientific literature, especially because policy makers change over time and newer colleagues may want to revisit previous work for a new campaign.
Prioritising interventions	Prioritise interventions according to available funding following the Danish Action Plan [43]	Identify interventions that: (1) can be initiated with the funds that are allocated to the loneliness strategy (2) can be initiated within existing financial frameworks  (3) should be initiated and require additional funding.
Work with funding bodies	Engage with funding bodies to ensure loneliness remains as a topic of relevance on the agenda	This collaboration can also influence how the funding priorities are laid out in the future. Additionally, collaborating with funding agencies can serve as a reminder of available funding opportunities and how to priorities interventions.
Revisiting previous campaigns	Revisit previous national and local campaigns to identify connection points for loneliness interventions	Cost and time effective way to include loneliness into the policy agenda. E.g. revisit campaigns on healthy aging, community development, welfare development, sustainable development, walkability, mental health.
Sharing best practice across borders	Promote cross-national collaboration to embed best-practice approaches	A cost-effective way to develop a strong knowledge base on which nations or regional governments around the world can build their context-specific loneliness strategies.
Setting out the vision	Have both a strategy to manage loneliness, and an action plan that details need for deployment of effective interventions (e.g. GB & DK)	This distinction helps build and sustain momentum on intervention strategies. Having a national suggestion on evidence-based interventions (or being open about which interventions are backed by evidence and which are not) may help local authorities to decide what kind of interventions best suit their context.
Evaluation of interventions	Local authorities should engage with central government when implementing and testing interventions that are not yet evidence-based	Evaluation is not always part of an intervention implementation yet it is essential to ensure that resources are not wasted by implementing ineffective interventions as there are still many knowledge gaps on the effectiveness of loneliness interventions. There should be funding allocated to evaluation of interventions.
Scalability of intervention	Decide if your planned intervention will need to be scalable or not and plan finances accordingly	Online loneliness interventions, such as described by [71], are more cost-effective to scale-up than in-person or community level interventions. Overall, there is a lack of evidence on scalable interventions for the general population and at-risk groups of loneliness [72].