Inclusion health focuses on people in extremely poor health due to poverty, marginalisation, and multimorbidity. This open access research, published in The Lancet, with researchers including a Pathway fellow and a Pathway Trustee, aimed to review morbidity and mortality data on four overlapping populations who experience considerable social exclusion: homeless populations, individuals with substance use disorders, sex workers, and imprisoned individuals. It found that these groups experience extreme health inequities across a wide range of health conditions, with the relative effect of exclusion being greater in female individuals than male individuals. It recommends that the high heterogeneity between studies should be explored further using improved data collection in population subgroups and calls for intensive cross-sectoral policy and service action to prevent exclusion and improve health outcomes in individuals who are already marginalised.