The paper posits that social determinants of mental health are the most modifiable targets for intervention to prevent mental health problems and disorders and promote positive mental health. These determinants encompass structural conditions across the life course influencing mental health outcomes and disparities. They include income, employment, socioeconomic status, education, food security, housing, social support, discrimination, childhood adversity, neighborhood conditions, and healthcare access. The distribution of these determinants is shaped by the distribution of money, power, and resources, often resulting in intergenerational inequities. Compelling evidence links the risk of developing mental health conditions to life circumstances, with those at the margins of society disproportionately affected. Improving population mental health through effective prevention strategies is presented as a central social justice issue. The authors note a critical juncture in understanding the causal role of modifiable social determinants and defining responses through effective prevention strategies that reduce inequities. While biomedical understanding of psychiatric disorders has advanced, investigating psychosocial factors has remained peripheral. The paper highlights the limitations in translating knowledge into effective clinical targets, with frontline treatments largely unchanged and treatment resistance prevalent. The last two decades have seen increased public awareness and advocacy, along with decreased stigma, leading to increased demand for mental health services but insufficient funding. This increased demand is not randomly distributed, reflecting existing social and economic inequalities. The paper specifically addresses the alarming rise in mental health problems among children and young people, attributing this to both period (e.g., COVID-19 pandemic) and cohort effects. These increases are also marked by inequalities across gender, socioeconomic status, and ethnicity. The paper advocates for integrating a social determinants perspective into the biopsychosocial model, requiring the establishment of causal links and understanding of mechanisms. This will strengthen the ability to develop and implement evidence-based prevention strategies that reduce inequities and improve population mental health.

The paper reviews the existing literature on the causal association between key social determinants and mental health and disorder. The focus is on determinants with broad effects on several major mental disorders globally, or those highly prevalent in society. These include individual and family-level determinants (socioeconomic disadvantage, discrimination, isolation, loneliness, early life adversities, childhood trauma) and wider social environment determinants (neighborhood disadvantage, social capital, physical environment, and climate change). The review pays particular attention to inequalities experienced by women, LGBTQ+ individuals, migrants, and ethnoracially minoritized groups. While acknowledging that the majority of the evidence comes from high-income countries in the Global North, the authors highlight available evidence from the Global South and recognize the need for dedicated attention to unique social determinants in diverse contexts. The review primarily uses quantitative evidence, acknowledging gaps in knowledge and challenges in establishing causality, particularly in observational studies.

The paper utilizes a systematic review approach to examine the evidence base concerning social determinants of mental health and effective prevention strategies. It first presents a review of the evidence supporting a causal link between key social determinants and mental health outcomes, concentrating on those with broad effects across major disorders or high prevalence. Individual-level determinants reviewed include socioeconomic disadvantage (operationalized across education, finance, occupation, and living standards), early life adversity (maternal stress, obstetric complications, malnutrition), childhood adversity (child maltreatment, household dysfunction), migration (push and pull factors, acculturative stress, discrimination), ethnoracial discrimination (interpersonal racism, microaggressions, structural racism), inequalities experienced by the LGBTQ+ community (discrimination, stigma, minority stress), and sex-based inequalities. Wider social environment determinants examined include neighborhood socioeconomic disadvantage and inequality, social capital (trust, reciprocity, networks), ethnic density, and physical environment (housing, pollution, green space, climate change). The review emphasizes the strong evidence for socioeconomic disadvantage's impact, with early life exposure being particularly harmful. The complexities of causal mechanisms are discussed, considering both social causation and social drift theories. The review also notes significant associations between early life adversity, childhood adversity, migration, discrimination, and mental health outcomes, along with the nuances and limitations of existing evidence. The paper then introduces a preventive framework for understanding how social determinants affect mental health at the population level, which can guide prevention strategies, including primary (universal, selective, and indicated) and secondary and tertiary prevention. A review of existing evidence on the efficacy of these strategies is then given. Interventions reviewed include parenting interventions, school-based mental health programs (mental health literacy, reducing stigma, reducing disruptive behaviour, mindfulness-based programs, suicide prevention programs), interventions addressing loneliness, direct economic interventions (guaranteed incomes, cash transfers), home visiting programs, neighborhood interventions (Moving To Opportunity program, neighborhood regeneration), and public mental health interventions for specific populations (refugees, ethnoracially minoritized groups, LGBTQ+ community). Specific secondary and tertiary prevention strategies reviewed include social prescribing, vocational interventions, family interventions, and trauma-informed interventions. The authors acknowledge the limitations and gaps in evidence, and especially the lack of high-quality longitudinal research for most interventions.

The paper's key findings highlight strong and consistent evidence for the association between several social determinants and mental health outcomes. Socioeconomic disadvantage, early life adversity, and childhood adversity are consistently linked to poorer mental health outcomes across the life course. Migration, ethnoracial discrimination, and minority stress are shown to disproportionately affect the mental health of various marginalized groups. Neighborhood-level factors like socioeconomic disadvantage, inequality, social capital, and ethnic density also influence mental health. Specific findings regarding individual determinants show consistent inverse associations between socioeconomic position and mental health problems in children and adolescents. Prenatal maternal stressors are linked to increased risk of several offspring mental health problems, while prenatal malnutrition is associated with increased psychosis risk. Childhood adversity demonstrates substantial associations with various mental health outcomes, including a substantial population-attributable risk. Regarding migrant groups, elevated psychosis rates are observed, but findings for other disorders are less clear, with potential explanations including selection effects and post-migratory experiences. Ethnoracial discrimination, through interpersonal racism and microaggressions, shows strong prospective associations with poorer mental health and various mental disorders. The LGBTQ+ community faces similar issues, with experiences of prejudice, stigma, and minority stress consistently associated with poor mental health outcomes. Sex-based inequalities in mental health are noted, with the complexity of biological and social factors highlighted. Loneliness and social isolation are both associated with depression and other mental health conditions. Findings for neighborhood-level social determinants highlight consistent evidence of increased risk of non-affective psychotic disorders in disadvantaged neighborhoods, although causal inference remains challenging. Socioeconomic inequality, rather than absolute deprivation, has been robustly associated with worse population mental health. Social capital and ethnic density are generally associated with better mental health, with some nuances and subgroup effects. Mixed findings emerge regarding the physical environment. The review of prevention strategies demonstrates the efficacy of various interventions, including parenting interventions, school-based programs, direct economic interventions, and programs specifically tailored to marginalized groups. However, the evidence base is weaker for some interventions, especially those targeting loneliness, neighborhood-level changes, and certain specific populations.

The findings address the research question by demonstrating the strong and consistent relationships between social determinants and mental health outcomes, while acknowledging the complexities of causality. The significance of the results lies in their implications for public mental health policy and practice. Prioritizing primary prevention strategies, particularly those targeting social determinants, is highlighted as crucial for reducing inequities and improving population mental health. The paper emphasizes that interventions targeting social determinants will have broader, positive impacts beyond mental health, improving physical and social outcomes. The preventive framework proposed offers a valuable tool for guiding the development and implementation of effective prevention strategies across various levels, and the review of existing evidence helps identify promising intervention targets. The authors' recommendations, particularly emphasizing social justice, provide a roadmap for policy changes. The significant increases in mental health problems, especially among young people, alongside the existing inequalities, underscore the urgent need for action.

This paper contributes significantly to the understanding of social determinants of mental health and effective prevention strategies. The authors strongly advocate for prioritizing primary prevention, grounded in social justice principles, to reduce mental health inequalities and improve population well-being. Future research should focus on strengthening causal inference methodologies, conducting larger studies in diverse populations, and rigorous economic evaluations of interventions. A greater emphasis on interdisciplinary collaborations and multi-sectoral approaches is also essential for translating research into effective policy and practice.

The authors acknowledge several limitations. The majority of evidence comes from high-income countries, limiting the generalizability to other contexts. While the review tries to include studies from LMICs, there are still knowledge gaps regarding social determinants in these settings. Establishing causality in observational studies remains challenging, and the evidence base for certain preventive interventions is still relatively weak. The heterogeneity across studies in terms of methodology and outcome measures also impacts the reliability of the findings. Finally, the authors note a potential for publication bias, particularly for some of the interventions reviewed.