The Population Health Intervention Research Initiative for Canada (PHIRIC) defines population health intervention research thus:

Population health intervention research involves the use of scientific methods to produce knowledge about policy and program interventions that operate within or outside of the health sector and have the potential to impact health at the population level.

“Impacting at a population level” means addressing the underlying social determinants and risk conditions that generate the health patterns. It also invites analysis of interventions that are intended to target everyone.

Intervention research came about to test ideas about causal mechanisms; the investigator (or “experimenter”) acts or intervenes in a putative causal pathway to test his/her idea about how variables are related to each other.  The investigator in PHIR can be the person designing and testing interventions- or they can be taking an observational role, by testing causal pathways and impact of interventions (polices and programs) designed and implement by others.

Intervention research is about all parts of the process of designing and testing solutions to problems and getting solutions into place – or any one piece of this.  It can involve process evaluation of interventions (assessing reach, implementation, satisfaction of participants, quality).  It can involve assessment of the contribution of context and how interventions adjust to different contexts.  It extends to assessment of how interventions are sustained over time or become embedded in the host institutions. It also includes diffusion research- or understanding how interventions are spread to new sites or taken up differently by different groups. It therefore identifies a specific population health intervention as its object of investigation either as an independent or as a dependent variable.

The methods of PHIR might be experimental, quasi experimental, observational, participatory, qualitative or quantitative (or both). Data sources might be primary or secondary.  Time frames might be prospective or retrospective.  By this definition, PHIR includes fields like health promotion research, program evaluation, policy analysis and health impact assessment.

Needs assessment, or research that generates ideas about possible interventions, is not PHIR.  This is because too much of population health research would be included if we defined PHIR this way and, more particularly, this type of work does not directly address the intervention itself.