When we think of climate change, a few things come to mind: ice caps, extreme weather events, and rising temperature, to name a few. What one might not think of is the profound impact it has had on mental health. From the anxiety sparked by extreme weather events to the stress of displacement, climate change is increasingly linked to rising rates of depression, anxiety, and trauma worldwide.¹

Children comprise one of the most vulnerable groups, with approximately one in six children and teenagers in the U.S. (aged 6 to 17) facing a mental health condition such as depression or anxiety.² One researcher, Dr. Perry Sheffield of the Icahn School of Medicine at Mount Sinai, sought to bridge the gap between those findings and recent reports of climate change influencing mental health. By measuring the amount hospital and emergency room visits during high temperature conditions, her research highlights how heat may impact the rate of acute mental health encounters among young people ages 6 to 25 in New York City. ³

While the mechanism through which heat exposure impacts mental health is not fully understood, scientists have proposed many different ideas. Some argue that it can exacerbate existing mental health conditions by altering thermosensitive physiological processes.³ “There is potentially a biochemical reason why hot weather might mess with your brain,” Dr. Sheffield said in an interview with Berkeley Scientific Journal. Studies show that heat can temporarily reduce serotonin levels, a neurotransmitter that affects mood, which may increase anxiety, fear, and aggression.⁴ Another way is through sleep, as inadequate sleep can aggravate mental health issues. A large-scale study, which analyzed ten billion sleep observations, found that rising nighttime temperatures are disrupting sleep worldwide, with the impact being three times more severe for people living in lower-income countries.⁵

Summarizing her interest in the field, Dr. Sheffield explained, “It was an area that I felt was underexplored… there was a lot of emerging work particularly about pollution and brain health, as well as acute mental health episodes.” She noted that extreme temperatures interested her because of their role as a corollary to air pollution, and what drew her to look at mental health and temperature was “the maxim of people being ‘cranky and hot.’” “That kind of thing piques my interest, finding out where these sayings come from,” she said, “there’s not always a pathophysiology behind it, but sometimes there is.”

In designing the study, she took into account that New York is one of the world’s largest urban centers. Specifically, Dr. Sheffield considered that cities are heat islands: areas that experience higher temperatures than those around them.³ This phenomenon occurs because buildings, roads, and other infrastructure absorb and re-emit the sun’s heat more than landscapes like water bodies and forests.⁶ She also investigated the often overcrowded conditions of the city as potentially driving acute mental health events. An additional focus was access to consistent air conditioning, as it could help explain racial disparities in the study’s result (Black and Latine populations were more vulnerable).

With all of that in mind, and after running statistical analyses on data from the New York City Department of Health, Dr. Sheffield and her team found that days of elevated temperature were associated with higher risk of mental health–related emergency department visits and hospital encounters among children, adolescents, and young adults alike.³ While the diagnoses most strongly associated with temperature differed by age group—reaction disorder, anxiety and bipolar disorders, and psychosis for children, adolescents, and young adults respectively—the theme that climate change is a significant contributing factor to the mental health crisis remained clear.

Dr. Sheffield’s research highlights the increasingly undeniable link between climate change and mental health. With rising temperatures contributing to mental health emergencies, especially in vulnerable populations such as children and adolescents, the impact of our changing environment goes beyond physical health. Ultimately, as the climate crisis worsens, addressing its mental health consequences will become ever more urgent.

References:

1. What happens when climate change and the mental-health crisis collide? (2024). Nature, 628(8007), 235–235. https://doi.org/10.1038/d41586-024-00993-x.
2. Whitney, D. G., & Peterson, M. D. (2019). US National and State-Level Prevalence of Mental Health Disorders and Disparities of Mental Health Care Use in Children. JAMA pediatrics, 173(4), 389–391. https://doi.org/10.1001/jamapediatrics.2018.5399.
3. Niu, L., Girma, B., Liu, B., Schinasi, L. H., Clougherty, J. E., & Sheffield, P. (2023). Temperature and mental health–related emergency department and hospital encounters among children, adolescents and young adults. Epidemiology and Psychiatric Sciences, 32, e22. https://doi.org/10.1017/S2045796023000161.
4. Bundo, M., Preisig, M., Merikangas, K., Glaus, J., Julien Vaucher, Gérard Waeber, Marques-Vidal, P., Strippoli, M.-P. F., Müller, T., Franco, O., & Vicedo-Cabrera, A. M. (2023). How ambient temperature affects mood: an ecological momentary assessment study in Switzerland. Environmental Health, 22(1). https://doi.org/10.1186/s12940-023-01003-9. ‌
5. How climate change affects mental health | News | Wellcome. (2023, November 8). Wellcome. https://wellcome.org/news/explained-how-climate-change-affects-mental-health.
6. Heat Island Effect | US EPA. (2014, February 28). US EPA. https://www.epa.gov/heatislands#:~:text=Heat%20islands%20are%20urbanized%20areas,as%20forests%20and%20water%20bodies.

Image Reference:

Cdc.gov. “How Climate Change Can Affect Your Mental Health | Blogs | CDC,” May 10, 2022. https://blogs.cdc.gov/yourhealthyourenvironment/2022/05/10/how-climate-change-can-affect-your-mental-health/. ‌