Food security and nutrition (FSN) are crucial for global health, yet access to healthy diets is often limited, particularly for low socioeconomic groups. This leads to undernutrition in low- and middle-income countries (LMICs) and nutrition-related chronic diseases (NRCDs) globally. While progress has been made in reducing hunger, food insecurity persists, and obesity rates are rising. Mental health is another major global health concern, with depression being a leading cause of disability. Although measuring the global burden of mental illness is challenging, the significant impact of depression, anxiety, and stress is undeniable. Both FSN and mental health research have evolved to consider broader environmental and contextual factors, leading to investigations into the complex interplay between them. Previous research has shown links between food insecurity and poor mental health, with mixed evidence regarding specific nutrients and dietary patterns. The association between BMI and mental health has been extensively studied, mainly in high-income countries (HICs). Furthermore, parental mental health, especially maternal, has been linked to children's nutritional status. Existing systematic reviews are often narrow in scope, focusing on specific populations and indicators. This study aims to comprehensively map the literature associating FSN with mental health, creating an interactive EGM to guide future research.

The researchers conducted a comprehensive literature review using three databases to identify analytical studies linking FSN to mental health. Existing research demonstrated associations between food insecurity and poor mental health across various contexts. However, evidence regarding the link between specific nutrients and mental health was inconsistent, with studies often hampered by the heterogeneity of measures and indices used. The relationship between BMI and mental health, although a long-standing area of inquiry, is predominantly based on research from HICs. Studies have explored the association between parental mental health and their children's nutritional status, with mixed findings across different settings. The limitations of existing systematic reviews, often narrow in scope and relying heavily on post-hoc analyses of observational studies, highlight the need for a more comprehensive overview of the literature.

The study employed a systematic search of three databases to identify analytical studies examining the relationship between FSN and mental health. The search strategy, developed by an information specialist, yielded 40,192 initial records. After removing duplicates and screening titles and abstracts, 3771 full-text articles were reviewed. 1945 studies met the inclusion criteria and were included in the EGM. The EGM incorporated a wide range of FSN constructs (food security, nutritional risk, diets, nutrient intakes, nutrient biomarkers, infant and young child feeding [IYCF], birth outcomes, and anthropometry) and mental health problems (depression, anxiety, stress, and mental well-being). The studies were categorized by various factors including study design, population, setting, and hypothesis tested. A PRISMA flowchart illustrated the study selection process. The data were presented in several ways, including a heat map showing the distribution of FSN and mental health measures, a Sankey diagram illustrating the relationships between FSN and MH categories, a choropleth map showing the geographic distribution of studies, and a bubble diagram showing the distribution across various population groups. The analysis also looked into the direction of the hypothesis tested (FSN as exposure vs mental health as exposure). Study designs were categorized as observational (cross-sectional, longitudinal, case-control), experimental (RCTs, quasi-experimental), and reviews (systematic reviews with/without meta-analysis). The geographic location of the studies was classified by HIC/LMIC and specific regions and countries. The populations of interest were categorized broadly (children, adults, pregnant/postpartum women, etc.) and the analysis also considered cases where FSN in one group was linked to mental health in another group.

The analysis of 1945 studies revealed that anthropometry (particularly BMI), and dietary patterns were the most frequently studied FSN measures linked to mental health. Depression was the predominant mental health outcome. A smaller proportion of studies examined IYCF, birth outcomes, and nutrient biomarkers in relation to anxiety, stress, and well-being. Most studies (66%) hypothesized FSN as the exposure, while 31% hypothesized mental health as the exposure. The majority of studies were observational (83%), with a smaller proportion being experimental (RCTs and quasi-experimental studies) or systematic reviews with meta-analyses. Studies from HICs, particularly the United States, Australia, and the United Kingdom, were overrepresented. Though approximately 23% of studies were conducted in LMICs, the representation of these countries did not reflect the global burden of FSN and mental health issues. The most common mental health measures were depression (using instruments such as CES-D, EPDS, GDS, and PHQ), while anxiety, stress, and well-being were less frequently studied. Significant gaps were observed in research on several aspects, including the relationship between various nutrients (e.g., selenium, antioxidants), IYCF, child growth, and mental health, along with a significant lack of experimental studies on interventions addressing multiple aspects of FSN and mental health. The analysis also highlights that studies focusing on the mental health of one population (e.g. mothers) and the FSN status of another (e.g., children) are predominant. Studies with less representation are those that assess the impact of mental health on women's nutrition or vice versa.

The EGM highlights a significant body of evidence linking FSN to mental health, particularly the association between BMI, dietary patterns, and depression. However, notable gaps exist, especially in research on anxiety, stress, well-being, and the influence of various nutrients, IYCF, and child growth on mental health outcomes. The overrepresentation of studies from HICs and the underrepresentation of LMICs present a significant limitation, as FSN and mental health challenges disproportionately affect LMIC populations. The paucity of experimental studies also limits our understanding of causal mechanisms and hinders the development of effective interventions. Qualitative studies are also underrepresented, meaning the lived experiences of individuals are not explored thoroughly. The EGM highlights the need for more research focusing on diverse populations, diverse settings, and other mental health outcomes beyond depression. Furthermore, research focused on integrating FSN and mental health approaches is critical.

This study presents the first comprehensive EGM mapping the existing research on the relationship between FSN and mental health. The map reveals significant gaps in research, particularly concerning LMICs, less-studied mental health conditions, and the design of effective interventions. Future research should focus on these gaps to improve the understanding and address the complex interplay between FSN and mental health globally. The interactive nature of this resource allows researchers and policymakers to easily identify and target critical areas needing attention, contributing to the development of more effective interventions and policies that promote both mental and physical well-being.

The study's limitations include the focus on English-language publications, the exclusion of grey literature, and the potential bias inherent in the databases used. The absence of a comprehensive quality assessment and the focus on published research rather than the full scope of potential findings might affect the generalizability of certain conclusions. While the large number of studies included in the analysis provides significant insights, the limitations above might lead to some biases and missed opportunities for a more comprehensive picture of the topic.