Understanding how heat affects mental health
As our planet continues to warm, we know rising temperatures affect physical and mental health. For every 1°C-increase in temperature (about 2°F), suicide rates rise about 1.7% and mental health hospital visits jump nearly 10% during heat waves compared to cooler periods.
As global temperatures have risen 1.2°C since the 19th century and are expected to climb 3.2°C more by 2100, it is essential that we develop effective ways to protect our psychological well-being.
Our previous research identified young adults ages 18-25 as the most vulnerable age group, with suicide rates increasing 3% for every 1°C increase in temperatures—an effect as large as what we see after major environmental disasters. This is why our current research focuses on that age group.
The problem we aim to solve
While we know heat affects mental health, we don't fully understand how it happens. We also don't know which aspects of heat exposure matter most—nighttime temperatures disrupting sleep, daytime heat making it hard to think clearly, or something else entirely? Understanding these pathways will help us develop solutions.
Over the next five years, we will conduct two studies to help us understand how heat affects mood and identify targets for intervention. We’ve designed these studies with input from young people who have lived experience with depression.
Study 1: Real-world monitoring
We'll work with 1,000 young adults across the U.S. experiencing summer depression. For one month, participants will wear small devices to continuously measure temperature and humidity around them, as well as sleep and activity trackers. They'll take regular phone surveys on their mood, depression symptoms and cognitive performance.
For the first time, we’ll see how temperatures people experience relate to mental health symptoms, sleep quality, ability to think, and physical activity in real-world settings.
Study 2: Controlled lab testing
In a smaller more intensive study, we'll do the same month-long monitoring but also bring 50 young adults with depression into a controlled lab environment for two weekends and randomly expose them to moderate and high temperature conditions while monitoring their brain activity, sleep patterns, body temperature, physical activity and mental health symptoms.
This controlled approach will help us understand the direct effects of temperature on mental health and figure out whether daytime or nighttime heat exposure has a bigger impact on mood.
Our studies will help us answer key questions:
- Does heat affect mental health by disrupting sleep, making it harder to think clearly, interfering with healthy routines like exercise or socializing, or through other pathways we'll discover during interviews with study participants?
- Does the timing of heat exposures – day or night - affect mental health differently?
- Do other factors - gender, race, education, income, geography, or medications - protect people against heat effects on their mental health or make them more vulnerable?
Understanding these connections will point us toward practical, affordable solutions to protect mental health during hot weather—things like cooling pillows, reflective window treatments or other ways to maintain good sleep during summer heat.