Background
Tackling challenges related to health, environmental sustainability and equity requires many sectors to work together. This “intersectoral co-operation” can pose a challenge on its own. Research commonly focuses on one field or is conducted within one region or country. The aim of this study was to investigate facilitators and barriers regarding intersectoral co-operative behaviour as experienced in twelve distinct case studies in ten European countries. The COM-B behavioural system was applied to investigate which capabilities, opportunities and motivational elements appear necessary for co-operative behaviour.

Method
Twelve focus groups were conducted between October 2018 and March 2019, with a total of 76 participants (policymakers, case study coordinators, governmental institutes and/or non-governmental organisations representing citizens or citizens). Focus groups were organised locally and held in the native language using a common protocol and handbook. One central organisation coordinated the focus groups and analysed the results. Translated data were analysed using deductive thematic analysis, applying previous intersectoral co-operation frameworks and the COM-B behavioural system.

Results
Amongst the main facilitators experienced were having highly motivated partners who find common goals and see mutual benefits, with good personal relationships and trust (Motivation). In addition, having supportive environments that provide opportunities to co-operate in terms of support and resources facilitated co-operation (Opportunity), along with motivated co-operation partners who have long-term visions, create good external visibility and who have clear agreements and clarity on roles from early on (Capability). Barriers included not having necessary and/or structural resources or enough time, and negative attitudes from specific stakeholders.

Conclusions
This study on facilitators and barriers to intersectoral co-operation in ten European countries confirms findings of earlier studies. This study also demonstrates that the COM-B model can serve as a relatively simple tool to understand co-operative behaviour in terms of the capability, opportunity and motivation required amongst co-operation partners from different sectors. Results can support co-operators’ and policymakers’ understanding of necessary elements of intersectoral co-operation. It can help them in developing more successful intersectoral co-operation when dealing with challenges of health, environmental sustainability and equity.