Food insecurity is characterized by limited or uncertain access to adequate food (Hamad and Khashroum, 2016). The coronavirus disease (COVID-19) pandemic that began in 2020 in the United States has substantially affected food systems. Statistics from the U.S. Department of Agriculture (USDA) showed that 10.5 % of the households (13.8 million) were food insecure at some time in 2020 and 10.2 % were food insecure at some time in 2021 (Economic Research Service, 2020). Pandemic-induced economic turndowns, high rates of unemployment, restricted lockdown, and fear of infection of the virus have greatly limited the availability, distribution, and utilization of food resources, which caused a 38.3 % increase in the national estimate of food insecurity at the beginning of the pandemic (Fitzpatrick et al., 2021). Disparities in food insecurity that existed before the pandemic may be exacerbated due to the unequal economic and health effects on socioeconomically disadvantaged communities (Katikireddi et al., 2021). For example, the unemployment rate among the Hispanic or non-Hispanic Black community was 2.7 %–6.9 % higher than that among the White community in the early days of the pandemic (Couch et al., 2020). Minority race/ethnicity groups with lower socioeconomic status also had higher risks of COVID-19 infection, hospitalization, and death (Khanijahani et al., 2021). Widened gaps in economic and health conditions for those disadvantaged populations raised important concerns regarding the loss of income and wealth, which may further lead to inequality in food insecurity.

The COVID-19 pandemic, a period of chronic and acute stress, also affected mental health (Collier Villaume et al., 2023). Clinically significant anxiety or depression was exhibited by 10 % to 40 % for all ages and was highest among young adults aged 18 to 29 years (anxiety: 40.4 %; depression: 36.3 %) throughout the pandemic (April 2020 to August 2022) (Collier Villaume et al., 2023). The prevalence of clinically significant anxiety or depression was 0.4 percentage points higher in the first year of the pandemic (2020) than before the pandemic (2017–2019) (Kessler et al., 2022). Recent studies have established associations between food insecurity and mental illness among the general US population during the COVID-19 pandemic (Polsky and Gilmour, 2020; Nagata et al., 2021; Lee and Singh, 2022; Zhu et al., 2023; Talham and Williams, 2023) and other populations such as older adults (Bergmans and Wegryn-Jones, 2023), children and adolescents (Dean et al., 2023; Smith et al., 2023), US soldiers (Beymer et al., 2021), Latinx adults (Trabilsy et al., 2024), and foreign-born immigrants (Li et al., 2023). However, there is very limited evidence on this association for communities who are more vulnerable to food insecurity such as young adults, females, individuals with children, and those with lower socioeconomic backgrounds (such as the Black, low-income, or unemployed individuals). Although the USDA reported an unchanged prevalence of food insecurity (10.5 %) for the overall US population in 2020 compared with that in 2019, the prevalence has increased for communities such as households with non-Hispanic Black people and households with children (2.6 % increase for non-Hispanic Black households and 1.2 % increase for households with children) (Economic Research Service, 2020). Besides, a significantly higher prevalence of food insecurity than the national average was observed in subgroups in 2020 including females (27.7 %), households with children (14.8 %), households with Hispanic (17.2 %) or non-Hispanic Black individuals (21.7 %), the unemployed (20.4 %), and the low-income individuals (28.6 %) (Economic Research Service, 2020). Young adults also reported higher odds of experiencing food insecurity than middle-aged or older adults (Nagata et al., 2021).

Additionally, a slightly higher prevalence of food insecurity was observed among the COVID-19-infected population than among the non-infected group (Kalantari et al., 2021; Cai and Bidulescu, 2023). A substantial proportion of the COVID-19-infected population also reported mental disorders such as anxiety (48 %, 95 % CI: 11 %, 85 %) or depression (38 %, 95 % CI: 24 %, 52 %) (Liu et al., 2021). However, it is less clear whether the association between food insecurity and mental illness is established for the COVID-19-infected who are vulnerable to both food insecurity and mental health conditions. Subgroup analyses are also needed for participants of nutrition assistance programs (such as the Supplemental Nutrition Assistance Program (SNAP)) due to the undetermined effects of food program participation on mental health: food resources and economic support provided for the participants could help mitigate their financial burdens and improve emotional well-being but may also increase feelings of shame or stigma (Gaines-Turner et al., 2019).

To fill in these research gaps, a cross-sectional study was conducted using the 2020 and 2021 National Health Interview Survey (NHIS) data. This study aimed to examine (1) socio-demographic disparities in food insecurity, and (2) the association between food insecurity and anxiety or depression symptoms in overall US adults and vulnerable communities including young adults (18–34 years), females, Hispanic people, non-Hispanic Black people, individuals with prior COVID-19 infection, the unemployed, individuals below the federal poverty line, individuals with children, and SNAP participants. Our results may inform targeted allocations of food benefits and mental health care resources, reduce disparities in food insecurity, and improve mental health, especially for disadvantaged communities.