Ideas, actors and institutions: lessons from South Australian Health in All Policies on what encourages other sectors' involvement.

<bold>Background: </bold>This paper examines the extent to which actors from sectors other than health engaged with the South Australian Health in All Policies (HiAP) initiative, determines why they were prepared to do so and explains the mechanisms by which successful engagement happened. This examination applies theories of policy development and implementation.<bold>Methods: </bold>The paper draws on a five year study of the implementation of HiAP comprising document analysis, a log of key events, detailed interviews with 64 policy actors and two surveys of public servants.<bold>Results: </bold>The findings are analysed within an institutional policy analysis framework and examine the extent to which ideas, institutional factors and actor agency influenced the willingness of actors from other sectors to work with Health sector staff under the HiAP initiative. In terms of ideas, there was wide acceptance of the role of social determinants in shaping health and the importance of action to promote health in all government agencies. The institutional environment was initially supportive, but support waned over the course of the study when the economy in South Australia became less buoyant and a health minister less supportive of health promotion took office. The existence of a HiAP Unit was very helpful for gaining support from other sectors. A new Public Health Act offered some promise of institutionalising the HiAP approach and ideas. The analysis concludes that a key factor was the operation of a supportive network of public servants who promoted HiAP, including some who were senior and influential.<bold>Conclusions: </bold>The South Australian case study demonstrates that despite institutional constraints and shifting political support within the health sector, HiAP gained traction in other sectors. The key factors that encouraged the commitment of others sectors to HiAP were the existence of a supportive, knowledgeable policy network, political support, institutionalisation of the ideas and approach, and balancing of the economic and social goals of government. [ABSTRACT FROM AUTHOR]