Inclusion health is an emergent approach that aims to address extreme health and social inequities. Target populations have common adverse life experiences and risk factors such as poverty and childhood trauma that lead to social exclusion.1 Consequently, these populations have extremely poor health, multiple morbidity, and early mortality.2 Compounding these problems are numerous barriers to accessing health services.3 The key aims of the inclusion health agenda are to highlight the magnitude and consequences of extreme inequity, the need for preventive and early intervention approaches, and improved access to essential services for individuals harmed by exclusion.
An agreed conceptual framework for inclusion health has not yet been developed.2 In this Review, we employ existing social exclusion,4 intersectionality,5, 6 and life-course epidemiology7 perspectives, which examine how factors accumulate and intersect over time and affect health. Risk factors such as substance use, rough sleeping, imprisonment, and exchanging sex for money or drugs are known to overlap among populations that are socially excluded1 and lead to extremely poor health outcomes.2 This underscores the need to better understand what interventions can effectively address and prevent the multiple and complex needs of socially excluded populations as a whole, rather than focusing on subpopulations defined by singular risk factors. Our Review aims to provide an overview of which individual and structural interventions are effective to tackle the extreme health needs of inclusion health target populations.
We defined the Review operationally using the populations, interventions, comparators, outcomes8 method. Populations with histories of substance use disorders (excluding alcohol, cannabis, and tobacco), imprisonment, sex work, and homelessness in high-income countries were identified as target populations on the basis of previous research in the UK, which showed a high degree of overlap between these groups1, 6 and the need to coordinate services for them.9 Other important excluded groups, such as migrants and transgender populations, were beyond the scope of this Review. Full search terms are shown in the appendix. Additionally, we report a public engagement workshop that included people with experience of social exclusion, which aided the interpretation of the review findings (panel 1).
Key messages
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People who are excluded from mainstream society, such as those experiencing homelessness, imprisonment, drug addiction, and sex work, have considerably higher rates of disease, injury, and premature mortality than the general population. Services need to tackle the so-called tri-morbidity of physical and mental illness, and addiction. Multiple evidence-based individual and structural interventions are available to prevent and address the excess burden of disease in these populations, but the need to translate and scale effective practice into action is crucial. Removal of barriers to access and uptake of services can be accelerated by involving people who have experience of social exclusion.
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Extreme exclusion is associated with frequent use of acute services, providing a strong economic case for preventive action, which complements the compelling social justice case. Research on routes into homelessness has revealed a high prevalence of childhood trauma, including exposure to abuse, neglect, domestic violence, and parental mental ill-health and substance use disorders. These adverse life experiences have a strong social gradient, such that the highest risks are found in low-income populations. The most effective upstream prevention policy is likely to be reduction of material poverty and deprivation, especially among families with children who are at high risk of maltreatment.
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Gaps in knowledge remain, particularly around interventions to improve upstream determinants of social inclusion, such as employment and education, which are also instrumental to long-term recovery from social exclusion. People who have experienced exclusion have identified appropriate housing as the most important intervention, and systematic reviews have established the effectiveness of this intervention for improving health and social outcomes.