Preserving and improving mental health is one of the world’s great challenges. In 2016, mental and substance use disorders affected more than 1 billion people worldwide, and made up 7% of all the global burden of disease. In the United States, in 2016, depression ranked 9th and 4th for males and females respectively among the top causes of premature death, with anxiety also 7th for females

The burden of mental health is not evenly distributed throughout society; for example, women are globally ‘nearly twice as likely as men to suffer from mental illness’. Displaced communities that have been forced to move are reportedly at a much greater risk of suffering from mental health conditions than those who have had greater choice of where and when they voluntarily migrate to. Minority communities in the United States also bear a disproportionate burden of mental health-related issues. Structural reasons exist for this burden in the United States; social and environmental determinants such as financial stress, lower quality of (and access to) health care and housing, lack of access to parks and green spaces and structural racism all serve to engender mental health disparities. 

Migration and climate change also impact mental health. Migration, whether forced or voluntary, driven by economic or other reasons, can cause considerable psycholoigical stress, through difficulties in language acquisition and adaptation, loss of social and family networks, overall pressures of adaptation, discrimination, economic hardship, administrative and bureaucratical burdens linked to the management of migration, administrative detention, lack of legal status, lengthy status attribution processes, and unequal access to services. The pathways between climate change and mental health are posited but less definitive; it has been hypothesised that anomalously higher temperatures are associated with higher levels of distress in younger people. Previous work has also established robust positive associations between rising temperatures and increased suicide as well as assaults. “Eco grief”, or the anguish felt from experiencing environmental degradation, contributes to risks of adverse mental health. 

The COVID-19 pandemic has resulted in unprecedented change and stress on all parts of society. As the COVID-19 pandemic took hold in the first half of 2020, much of the world went into lockdown due to governmental orders and travel restrictions. Most time in the day had to be spent at home and indoors; outdoor travel was typically only allowed for essential workers, brief outdoor exercise and picking up essential supplies. The global population largely stopped travelling

Changes due to the COVID-19 pandemic are likely to impact public health beyond the deaths caused directly by infection, through loss of jobs and income; disruption of social norms and networks; changes in patterns of crime and self-harm; changes in quantity and quality of food, and the use of tobacco, alcohol and other drugsmore time interacting with the same peoplelack of green space accessincreased screen time; changes in mobility and transport patterns; and a general loss of purpose in life. The total excess mortality of COVID-19 is also almost certainly more than is currently being counted as COVID-19 excess mortality. These factors and others are likely to put a strain on the mental health of members of society. The full impact of the COVID-19 lockdown on mental health is actively being researched and investigated. The impact of COVID-19 on mental health also varies by agesexsocioeconomic status and race/ethnicity, with the latter in the United States largely due to historical racism and racist policies

Climate change and environmental degradation are likely to increase the frequency of future pandemics. One example of the impact on pandemics such as COVID-19 is how deforestation and a warming environment affect animal habitats, forcing species to look for new homes. This can result in interactions with not-previously-encountered pathogens, which make it more likely that deadly infectious outbreaks occur. Climate change may therefore impact mental health by causing weather conditions to change, while also providing a pathway which increases the probability of a pandemic. 

The cascading impacts of COVID-19 (and pandemics in general), climate change and migration all affect mental health in complex ways. The impact of each of these phenomena on mental health alone would be considerable; the combination of all three here creates a unique challenge of cascading impacts, but one which needs to be understood and addressed now and in the post-COVID-19 age. 

Aims and objectives 

Our aim is to provide a formalised framework of how climate change, migration and COVID-19 impact each other and mental health, to stimulate further research and action in this area. We have three objectives that will help us achieve this aim: 

  1. Conceptually introduce how interactions between COVID-19, climate change and migration exacerbate mental health outcomes via a directed acyclic graph (DAG) and cascading impacts and compound disasters; 

  1. Explain how research supports a policy-forming process in this particular context, with some case study examples; and 

  1. Identify provisional recommendations based on available evidence. 

We focus on case studies in the United States, as it is the world’s worst-hit country during the COVID-19 pandemic, with many serious structural issues present in society. Nevertheless, these case studies are relevant to many other countries. 

Directed acyclic graphs (DAGs) 

We utilise a directed acyclic graph (DAG) to detail causal mechanisms between phenomena (see Figure 1). DAGs are graphical tools, which have been used to represent relationships across a diversity of fields, ranging from computer sciencemedical science and epidemiology. DAGs provide a visual and straightforward way of representing causality in determining an unbiased estimate of effect of an exposure on an outcome. A DAG provides a simple way of visualizing interactions and relationships between climate change, migration, mental health and pandemics. 


Figure 1: Directed acyclic graph (DAG)

The DAG in Figure 1 is an illustration of how further research may explore the impacts of climate change, pandemics and migration on mental health. These future studies may take the form of studying cohorts (i.e., tracking individuals over time) or ecological (i.e., tracking community- or population-level health across time). The exposures in the DAG in Figure 1 are climate change, pandemics, weather regimes and migration. The outcome in our DAG is mental health. 

In the context of the DAG in Figure 1, the unit of analysis and the observability of each element should be considered and identified. For example, in an ecological study, the unit of analysis could be a country or region. The mental health outcome might be the prevalence of mental illness diagnoses in the unit of analysis. The observable of pandemics may be, for example, whether or not the unit of analysis is in a pandemic or not, or the prevalence of a pandemic’s disease. As with previous studies, these future studies may include stratification of a unit of analysis, which would provide a way to examine effect modification by, for example, age and sex. 

Pandemics like COVID-19 - Cascading impacts and compound disasters 

COVID-19 emerged into an already-complex world of risk, with disasters such as extreme weather, conflict and humanitarian crises, regularly causing national and regional disruption. Recent environmental disasters, such as the wildfires, flooding and drought in California,22 demonstrate how dangerous simultaneous disasters can be for the human environment system in the United States. Climate-related compound events occur when a combination of processes lead to an amplified impact. They can lead to multiple failures of essential infrastructure, such as electricity systems, which would, for example, have an impact on communication networks. Adverse impacts from human-induced climate change are likely to exacerbate fragilities in infrastructure, and could lead to multiple system breakdowns. Those already vulnerable to the worst impacts of climate change are also likely to be the most vulnerable to COVID-19; poorer parts of the world, poorer communities in industrialised countries, and those affected by environmental racism are at greater relative risk than more prosperous and advantaged communities

Here, we extended the idea of cascading and compound stressors on mental health to include the pandemic of COVID-19 and migration (Figure 1). Beyond the risk of death, COVID-19 adds psychological stress. COVID-19 and disruptions in existing migration also add strains to existing social systems, e.g., by interrupting low and unstable income streams for the migrants of pressure on existing systems of care, which are not currently optimised for unexpected shocks or indeed to take care of an entire population. This is particularly true in the United States, where, as of July 2020, there are over 3 million confirmed cases of COVID-19, with many more cases that have gone undetected. 

The compounding effect of multiple serious and simultaneous natural hazards along with COVID-19 and other pandemics, in tandem with the impact of a changing climate on those migrating and the communities they arrive at, puts strain on a society’s ability to cope with the negative impacts of compounding vulnerabilities. The oncoming heat wave and storm seasons will provide further strain to already-stretched health services, and may also act as effect modifiers from exposure to COVID-19 and the likelihood of death. 

Case studies 

Here we take a case study approach to characterise cascading impacts of COVID-19 in three embedded studies on i) seasonal migration, ii) urban setting and iii) socioeconomic status (SES) of migrants. We apply the theoretical framework outlined in the following case studies to exemplify worsening contextual vulnerability conditions of different types of extreme weather and climate-related migration, and mental health due to the COVID-19 pandemic. 

i) Seasonal migration 

The United States hosted the second highest number of international migrants in 2019; international migrants make up for 15.4% of the United States population. Seasonal migration from Mexico is primarily motivated by economic reasons, even though estimates show climate change could prompt broader out-migration from Mexico. The dynamic nature of the United States economy has propelled demand for seasonal migrants in agriculture, the manufacturing and construction and service industry since the 1970s. 

Central America and the Caribbean is one region where extreme weather-related migration to the United States has been particularly pronounced in the context of hurricanes. Hurricane Harvey, an exceptionally strong hurricane in 2017 affected Houston and can be attributed to human-induced climate change. With sea level rise, migration towards inland areas immediately adjacent to the coast could experience the largest incoming migrants - Houston and Dallas as two examples. There are numerous immigrants from the Americas region in the United States, a large migrant network that eases the way for those affected by hurricanes to migrate to family members who can sponsor them to come to the United States or provide other assistance to facilitate migration. As extreme weather events are likely to increase in frequency and intensity as a result of climate change, we might see more seasonal migrants who lose their homes in climate change hotspot regions turn to permanent migration as a way of adaptation, for instance in the context of sea level rise

The United States, like many other countries around the world, closed their borders for non-essential travel in March. Seasonal migrants from Mexico and Central America who are predominately employed in service and production type occupations face additional hardship: many of these migrants rely on visas and open borders between the country of origin and destination for employment and sending remittances to their families. The Department of Homeland Security acknowledges the need for seasonal migrants to maintain the country’s economy and food security and has paused its rule on the maximum allowable period of stay. In the case of agriculture related work, if migrant workers are unable to travel to agricultural fields and these restrictions are paired with broader disruptions to the global food supply chain, it might compound longer-term impacts on food security globally. However, efforts to keep seasonal migration channels open would require the buy-in of both countries of origin and destination. As an example, Guatemala has already cited public health concerns to curb the travel of their nationals to the United States. As such, the current pandemic might pave the way for rethinking operations on a broader scale that could have lasting implications for seasonal labor migration under a changing climate. 

ii) Urban setting 

The outbreak of COVID-19 in New York illustrates how frontline workers are among the worst hit from the ongoing pandemic. Already in the aftermath of Hurricane Sandy when the subway system was flooded and eventually shut down, New Yorkers suffered from adverse mental health effects; the severity however depended on exposure, risk and resilience of psychological distress, and intervention and treatment. In addition, the interrelationship between sociodemographic factors, climatic change, migration, and COVID-19 can play a major role in the mental health outcomes. 

Since the outbreak of the COVID-19 pandemic, it has become evident that urban areas are epicentres of COVID-19 cases and deaths across the United States. Hot spots have erupted in a few places with large outbreaks, none more dire than in New York, where at least 350,000 cases have been reported and at least 29,000 people have died since March 14. West Coast States, despite being as heavily populated as East Coast ones, have seen fewer infected people and reported fewer deaths from COVID-19. Public transportation and an inability to implement physical distancing in urban spaces could have contributed to a contrasting picture of COVID-19 on the East and West Coast.  

In the pre-COVID-19 years of 2017 to 2018, only 25 percent of U.S. workers were estimated to be able to transition to remote work. In addition, sharp differences exist across race and ethnicity; African Americans and Hispanic workers are among those least likely to work from home. There is a strong need for essential workers to leave their home, relying on public transportation to get to their places of work. In New York, immigrant workers are a significant percentage of essential workers, often without healthcare coverage. New Yorkers, whether foreign-born or not, rely on public transportation, commuting in the often-tightly packed spaces of a subway car. Here, riders are unable to follow the local government’s guidelines of physical distancing which has further implications for key workers and essential businesses. Inability to get to work might have contributed to higher unemployment rates, currently at an all-time high of 15% in New York State alone. Individuals losing their job, filing for unemployment, hiring freeze, perhaps even facing homelessness are at higher risk of distress and mental health issues. Effects of cascading failures from economic hardship go beyond unemployment per se and are interlinked with contextual factors such as gender, family responsibilities and social class, even adverse impacts on the treatment of children

iii) Socioeconomic status   

Socioeconomic status (SES) attributes range from quality of life and education, financial and societal standing, as well as overall health. Deeply intertwined connections between race, ethnicity and a person’s socioeconomic status, SES inequality impacts manifest in human wellbeing, physical and mental health. Racial and ethnic minorities have worse overall health; health disparities stem from cascading effects including economic determinants, education, geography and neighbourhood, environment such as air quality, lower quality or inadequate access to care, an inability to navigate the system, provider ignorance or bias, and stress. 

During Hurricane Katrina, the worst damage was predominately found in poor and African American neighborhoods, forcing them to leave their homes and delaying returns. Yet, disaster relief for these displaced communities was far slower and inadequate compared with that provided in predominantly higher-income neighborhoods, despite those suffering from less impacts.  

Quantifying nationwide disparities in locations of poor air quality, a study finds that poor people carry a 1.35 times higher burden of being exposed to particulate matter, which refers to a combination of solid and liquid particles in the air, compared with the overall U.S. population; the risk is even higher for communities of colour (1.54 times). Disparities manifest in geographical and socio-economic standing and are far more pronounced for people of colour. Previous studies have also linked the disproportionate exposure to poor air quality and racial demographics. Disproportionate exposure to poor air quality can be further exacerbated for communities of colour in adverse environmental conditions; for example, in fracking waste sites which can degrade water quality. Even though poor air quality might be generally worse in cities, air pollution can also affect nonurban areas. In Midwest rural communities, disproportionate burdens to adverse exposures of poor air quality are estimated to be a pathway to ethnic disparities in health and health care.  

Already, these disparities have led to environmental and health crises that fall along socio-economic and racial lines in communities across the United States. Anyone is at risk from the COVID-19 pandemic. But some parts of the population are more vulnerable; the elderly, those with chronic disease or disabilities, ethnic minorities and migrants. It can be expected that migrants who have experienced economic, environmental and health-related shocks in their past, will face additional mental health burdens in a post-COVID-19 recovery.  

Towards a better understanding of the mental health-migration-climate change nexus and COVID-19  

We set out to consider the extent to which mental health affects migrants in a rapidly changing climate. The case studies we consider here do not grasp the whole story of mental health issues in migration during COVID-19. However, they allow to draw a first set of recommendations to mitigate cascading impacts of the current pandemic.  

Synergies between research and policy 

As a first option to respond to the cascading impacts of the current crisis, human and mental health issues should be holistically considered in climate migration research, the advancement of migration concepts and related frameworks for policy makers. Practically speaking, research communities and practitioners could jointly work on scenario analyses of cascading impacts to develop feasible intervention points in multiple levels of policy action, i.e., top-down and bottom-up approaches. Realising research synergies is crucial for understanding differential impacts on mental health for different communities and geographic settings, and prioritizing action for those most affected.  

Data and way forward 

In addition to traditional data sources for epidemiological studies such as health and weather records, adding to the integrated intervention approach, we recommend using citizen science and crowdsourcing for data collection. This could help the preparedness of future interventions on cascading impacts from compound disasters. Mobile phones could provide one way to easily collect data on a large scale; for example in countries like the United Kingdom and France, where COVID-19 cases have spiked compared to neighbouring countries. Crowdsourced data collection efforts can be critical to inform integrated interventions in the future. Anticipatory action, an ex-ante approach of disaster preparedness, can also provide an effective way forward to utilise collected data for forecasting spread and magnitude of extreme events and compound disasters. For example, an anticipatory needs analysis can in turn provide timely evidence to plan a coordinated response focusing on different vulnerabilities of communities. 

Integrated intervention approach 

One option would be to provide free mental health support for migrants and other populations vulnerable to climate change. Seasonal migrants would benefit from being in good state of mental health while supporting the economy, obtaining paid work and being able to send back remittances. Tele-therapy provides a suitable intervention point to mitigate any mental health issues migrants might suffer from in response to pre-existing climate and weather shocks, and the cascading impacts of COVID-19. At the moment, psychotherapists do not count as essential workers in the United States and could continue working remotely by providing therapy sessions via phone or online. In parts, this has shown positive effects in the context of depression across the United States already. 


Utilizing three case studies, we show how COVID-19 acts as a risk multiplier and exacerbates already existing health disparities. In particular, cascading impacts could potentially compound and severely affect migrant’s mental health, when the privilege to fully engage in physical distancing is not available. 

Our generalised DAG framework details causal mechanisms between phenomena relevant to mental health (Figure 1), which helps focus research priorities on mental health, now and into the future. 



Robbie M Parks was supported by the Earth Institute post-doctoral research fellowship at Columbia University.

Lisa Thalheimer was supported by funding from the German National Member Organisation (NMO) as part of the Young Scientist Summer Program (YSSP) at the International Institute of Applied System Analysis (IIASA), and the Robertson Foundation (United States, award #9907422).

We thank Tom Bond for advice and guidance on DAGs.  


About the authors

Robbie M Parks, the Earth Institute, Columbia University, New York, New York, USA and Department of Environmental Health Sciences, Mailman School of Public Health, Columbia University, New York, New York, USA.

Lisa Thalheimer, Environmental Change Institute, University of Oxford, Oxford, UK and International Institute for Applied Systems Analysis, Laxenburg, Austria



This article is part of the IOM Series on The COVID-19 Pandemic, Migration and the Environment.

SDG 3 - Good Health and Well Being
SDG 13 - Climate Action