Understanding action on the social determinants of health: a critical realist analysis of in-depth interviews with staff of nine Ontario public health units

BACKGROUND: Addressing the social determinants of health (SDH) is identified as a role for local public health units (PHUs) in the province of Ontario. Despite this authorization to do so there is wide variation in PHU practice. In this article we consider the factors that shape local PHU action on the SDH through a critical realist analysis. METHODS: Interviews with Medical Officers of Health (MOHs) and lead staff from nine PHUs in Ontario identify the structures and powers that allow PHUs to address the SDH as well as the many factors that either activate or inhibit these structures and powers. RESULTS: We found that personal backgrounds and attitudes of MOHs and leading staff people as well as local jurisdictional characteristics shape whether and how PHUs carry out SDH-related activities. CONCLUSIONS: Action on the SDH is a result of a complex interplay of micro-, meso- and macro-level factors that requires recognition of the contested nature of public health, presence of Ministry of Health mandates, local jurisdictional characteristics, and politics. The most effective way to assure PHU action on the SDH is for the Ministry of Health and Long-Term Care to mandate such activities and develop accountability mechanisms that assure implementation.