A team of SHP faculty and researchers, together with Stanford Medicine graduate and medical students and in collaboration with colleagues at CIDE in Mexico, have launched a modeling framework to investigate the epidemiology of COVID-19 and to support pro-active resource planning and policy evaluations for diverse populations and geographies — including California, Mexico and India.

The Stanford-CIDE Coronavirus Simulation Model — or SC-COSMO — incorporates realistic demography and patterns of contacts sufficient for transmission of the virus that has infected more than 2 million people worldwide and claimed more than 125,600 lives, according to the widely used Johns Hopkins COVID-19 map which is updated several times a day.

The SC-COSMO model also incorporates non-pharmaceutical interventions, such as social distancing, timing and effects on reductions in contacts which may differ by demography.

Jeremy Goldhaber-Fiebert, an associate professor of medicine at Stanford Health Policy, is the principal investigator of the project, along with Fernando Alarid-Escudero, an assistant professor at the Center for Research and Teaching in Economics (CIDE) in Mexico and Jason Andrews, an assistant professor of medicine (infectious diseases) at Stanford Medicine. Other SHP faculty among the 20 investigators and staff members who are working on the project are Joshua Salomon and David Studdert, both professors of medicine.

The SC-COSMO team is a multi-disciplinary, multi-institutional team including expertise and experience in infectious disease, epidemiology, mathematical modeling and simulation, statistics, decision science, health policy, health law and health economics.

“As COVID-19 transmission occurs throughout the world’s diverse populations, it is critical to efficiently model and forecast its future spread between and within these populations and to appropriately reflect uncertainty in modeled outcomes,” Goldhaber-Fiebert said. “Doing so supports timely resource planning and decision making between potentially appropriate and effective interventions that balance the trade-offs they embody.”

The team is currently working on three projects:

1. The researchers are providing California with county-level COVID-19 estimates for such things as the number of infections, detected cases and projections of future needs for hospital and ICU beds, personal protective equipment (PPE) and ventilators.
2. The project is working on potential strategies to mitigate the COVID-19 pandemic in Mexico by focusing on three specific objectives: collecting, synthesizing and openly sharing the most relevant and useful data; accelerating the development of the SC-COSMO model and its adaptation to the Mexican situation; and identifying a set of mitigation strategies, comparing the health and economic consequences in the population in the medium and long term.
3. They are developing forecast models of the COVID-19 epidemic in India with the Wadhwani Institute of Artificial Intelligence and its Indian government partners, providing a rapid response to urgent needs for planning and resource allocation.

By comparing historical temperature and suicide data, researchers found a strong correlation between warm weather and increased suicides. They estimate climate change could lead to suicide rate increases across the U.S. and Mexico.

Suicide rates are likely to rise as the earth warms, according to new research published July 23 in Nature Climate Change. The study, led by Stanford economist Marshall Burke, finds that projected temperature increases through 2050 could lead to an additional 21,000 suicides in the United States and Mexico.

Researchers have recognized for centuries that suicides tend to peak during warmer months. But, many factors beyond temperature also vary seasonally – such as unemployment rates or the amount of daylight – and up to this point it has been difficult to disentangle the role of temperature from other risk factors.

“Suicide is one of the leading causes of death globally, and suicide rates in the U.S. have risen dramatically over the last 15 years. So better understanding the causes of suicide is a public health priority,” Burke said.

Heat and suicide

To tease out the role of temperature from other factors, the researchers compared historical temperature and suicide data across thousands of U.S. counties and Mexican municipalities over several decades. The team also analyzed the language in over half a billion Twitter updates or tweets to further determine whether hotter temperatures affect mental well-being. They analyzed, for example, whether tweets contain language such as “lonely,” “trapped” or “suicidal” more often during hot spells.

The researchers found strong evidence that hotter weather increases both suicide rates and the use of depressive language on social media.

“Surprisingly, these effects differ very little based on how rich populations are or if they are used to warm weather,” Burke said.

For example, the effects in Texas are some of the highest in the country. Suicide rates have not declined over recent decades, even with the introduction and wide adaptation of air conditioning. If anything, the researchers say, the effect has grown stronger over time.

Effect of climate change

To understand how future climate change might affect suicide rates, the team used projections from global climate models. They calculate that temperature increases by 2050 could increase suicide rates by 1.4 percent in the U.S. and 2.3 percent in Mexico. These effects are roughly as large in size as the influence of economic recessions (which increase the rate) or suicide prevention programs and gun restriction laws (which decrease the rate).

Effects of historical temperature changes on suicide rates are shown for the U.S. and Mexico. (Image credit: Marshall Burke)

Effects of historical temperature changes on suicide rates are shown for the U.S. and Mexico. (Image credit: Marshall Burke)

“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot. Now we see that in addition to hurting others, some individuals hurt themselves. It appears that heat profoundly affects the human mind and how we decide to inflict harm,” said Solomon Hsiang, study co-author and associate professor at the University of California, Berkeley.

The authors stress that rising temperature and climate change should not be viewed as direct motivations for suicide. Instead, they point out that temperature and climate may increase the risk of suicide by affecting the likelihood that an individual situation leads to an attempt at self-harm.

“Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide,” Burke emphasized. “But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm.”

Marshall Burke is also a fellow at the Center on Food Security and the Environment, Stanford Woods Institute for the Environment, Freeman Spogli Institute for International Studies, and Stanford Institute for Economic Policy Research. Solomon Hsiang is also a faculty research fellow at the National Bureau of Economic Research. Other Stanford co-authors include Sanjay Basu, assistant professor of medicine, and Sam Heft-Neal, research scholar at the Stanford Center on Food Security and the Environment. Additional co-authors are from Pontificia Universidad Católica de Chile, Vancouver School of Economics, and the University of California, Berkeley. The research was partially supported by the Stanford Woods Institute for the Environment.