Three Subtle Ways Climate Change Degrades Your Mental Health

And it’s not just humans who become hostile and agitated in extreme heat. Dogs are more prone to biting on hot, sunny days, while other species, from magpies to bumblebees, become confused and function poorly. 

Granted, most research on extreme heat and mental health looks at the relationship between, say, weather data and crime stats, but it can’t prove cause-and-effect. Experimental studies are few. In one, police officers training in an uncomfortably hot room were more likely to draw and fire their weapons than their colleagues training in cooler conditions. 

Such studies are complicated and expensive and can be unethical, Anderson said. No one wants to subject volunteers to extreme heat, give them weapons, and see what happens.

Yet certain physiological mechanisms provide a biological basis for emotional changes in heat. For one, we tend to sleep worse when the mercury is high, and “sleep is very closely linked to mental health outcomes,” said Emma Lawrance, PhD, a clinical neuroscientist at the Imperial College London. A 2021 review linked restless nights to more frequent negative moods, increased irritability, and deterioration of mental health conditions such as schizophrenia. 

Know that some mental health medications – such as tricyclic antidepressants and psychotropic drugs — “can interfere with the body’s ability to regulate temperature,” Lawrance said, potentially making the heat’s effects worse. “While it’s very, very important people continue to take their medication, it’s very important people also have the right information about how to keep themselves safe,” Lawrance said. In other words: Talk to your doctor. 

Extreme weather events, such as hurricanes, can also stir up brain-harming pollutants in the water we drink and the earth where we grow our food. Hurricane Harvey left soils around Houston contaminated with heavy metals such as lead, while Hurricane Maria added several pesticides and arsenic to Puerto Rico’s drinking water. 

Lead has long been linked to cognitive challenges — from lower IQ to depression and mania. Other heavy metals, such as cadmium, are associated with mental health disorders. As such, drinking bottled water is recommended after hurricanes. 

Cognitive Effects of High CO2

As climate change progresses, rising carbon dioxide levels are an obvious marker. What’s less obvious is how CO2 increases can affect our ability to think. 

“It’s another, indirect reason to not want to burn fossil fuels,” Ranney said. CO2 concentration in the atmosphere has already increased from about 280 ppm in pre-industrial times (mid-1700s) to 419 ppm in 2023. At this rate, it could more than double by the year 2100, exceeding 900 ppm. 

Lab experiments show that such high doses of CO2 may impact how clearly we think. In one study, people’s decision-making suffered when they were exposed to 1,000 ppm CO2 – they were less flexible in solving problems and had trouble using information to make a decision. In another, a 400 ppm increase in CO2 was associated with a 21% decrease in cognitive function (the ability to learn, think, and reason). 

As Ranney points out, volunteers in these experiments are exposed to high CO2 for short periods of time — say, a couple of hours. “If that can diminish one’s cognitive performance, imagine what it’s like if you never have a respite,” he said. 

Ranney suspects that human cognition may already be impacted by the atmosphere’s heightened CO2. And the higher the CO2 level is outside, the harder it is to keep air fresh inside, where CO2 can easily climb to more than 1,000 ppm. 

What to Do:

Although we can’t simply scrub CO2 out of the air, we can try to keep indoor levels as low as possible. 
Use a carbon dioxide monitor, and if the levels exceed 1,000 ppm, open the windows if air quality is not bad that day. Avoid using unvented or poorly vented fuel-burning appliances, such as gas stoves or space heaters. Some studies also suggest that potted plants may help reduce CO2 levels at home, especially if provided with plenty of light. 

Still, while these tips can help you protect yourself, what we really need, Lawrance said, is urgent action on climate change. “Creating a world that is cleaner is … much better for our mental health,” she said.    

SOURCES:

Emma Lawrance, PhD, clinical neuroscientist, Imperial College London. 

Michael Ranney, PhD, cognitive psychologist, University of California, Berkeley. 

Craig Anderson, PhD, psychologist, Iowa State University, Ames.

Paul Wennberg, PhD, atmospheric chemist, California Institute of Technology, Pasadena.