Exposure to excessive heat appears to hinder psychological development

New research has found that early childhood exposure to high ambient temperatures may hinder the development of foundational skills. The findings indicate that children living in environments with average maximum temperatures exceeding 32 degrees Celsius, or roughly 90 degrees Fahrenheit, are less likely to reach developmental milestones, particularly in literacy and numeracy. This study was published in the Journal of Child Psychology and Psychiatry.

Global temperatures reached record highs in 2024, raising concerns about the cascading effects of a warming planet on human health. Previous scientific inquiries have established links between extreme heat and various physical ailments in both children and adults. Less is known regarding how heat exposure during the formative years of life affects cognitive and psychosocial growth.

The first few years of life represent a sensitive period for brain maturation. Biological systems in young children are not fully developed, making them less efficient at regulating body temperature through mechanisms like sweating. Young children also rely entirely on adults to modify their environment or provide hydration.

Heat may disrupt development through several biological and ecological pathways. High temperatures can cause dehydration and sleep disruption, both of which are detrimental to learning. Heat stress can also trigger neuroinflammation and heighten the body’s stress response systems.

Beyond direct physiological effects, heat can alter a child’s environment. Extreme weather can compromise food security by damaging crops or increasing food contamination risks. It may also increase the prevalence of disease vectors, such as mosquitoes, leading to illnesses that stunt growth.

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“We know extreme heat affects physical health, but there was very limited evidence on how it shapes early child development, especially in low- and middle-income settings. This study addresses that gap by showing that heat exposure is also a developmental risk factor during early childhood,” said study author Jorge Cuartas, an assistant professor at New York University and co-director of Fundación Apapacho.

To investigate these potential impacts, the researchers utilized a large dataset comprising 19,607 children. The participants were three and four years old. They resided in six diverse nations: Georgia, The Gambia, Madagascar, Malawi, Sierra Leone, and the State of Palestine.

These specific countries were selected based on the availability of precise data. The researchers needed geolocated household clusters that also contained detailed information on child development. The data collection took place between 2017 and 2020.

The investigators combined survey data with high-resolution climate records. They used the Early Childhood Development Index (ECDI) to assess the children’s progress. This index is a standardized tool developed by UNICEF to track developmental milestones.

The ECDI relies on parent reports regarding specific skills and behaviors. It covers four distinct domains: literacy-numeracy, physical development, social-emotional functioning, and approaches to learning. A child is considered “on track” if they can perform a majority of the tasks in a given domain.

For climate data, the team used the ERA5-Land Monthly Aggregated Climate Dataset. This allowed them to calculate the mean monthly maximum temperature each child was exposed to from birth until the date of their interview. The researchers matched the geographic coordinates of each child’s home cluster with historical weather patterns.

The statistical analysis employed linear probability models. The researchers included geographic and seasonality fixed effects. This means they compared children living in the same subnational regions who were born at different times of the year, rather than comparing children across vastly different climates.

This approach helped account for baseline differences between hot and cold regions. It allowed the researchers to isolate the specific effect of temperature anomalies and sustained heat exposure. They also controlled for variables such as household wealth, maternal education, and whether the home was in an urban or rural area.

The analysis revealed a negative association between high heat and overall development. Children exposed to average monthly maximum temperatures above 32 degrees Celsius were less likely to be developmentally on track. This effect persisted even when the researchers accounted for baseline climate conditions and socioeconomic factors.

“Extreme heat doesn’t just make children uncomfortable; it can quietly interfere with how they learn, communicate, and develop basic skills,” Cuartas told Psypost. “As heat waves become more common, protecting children from heat exposure is increasingly a developmental issue that might have long-term consequences for individuals and societies.”

When the researchers broke the data down by specific domains, the results varied. The negative impact of heat was most evident in literacy and numeracy skills. Children exposed to the highest temperatures showed a statistically significant drop in these cognitive milestones compared to those in cooler environments.

The researchers also found a link between heat and lower social-emotional scores at 32 degrees Celsius. However, this association was not consistent across all higher temperature brackets. Physical development showed a slight positive association with moderate warmth but no clear trend at extreme highs.

The results highlighted significant inequalities regarding who is most affected by rising temperatures. The burden of heat was not shared equally across all demographics. Children from economically disadvantaged households showed a steep decline in developmental scores as temperatures rose.

In contrast to the poorer households, children from wealthier families did not exhibit the same negative trajectory. This suggests that financial resources may provide a buffer against the detrimental effects of heat. Wealthier families might have better access to cooling technologies or better nutrition to counteract heat stress.

Geography and infrastructure also played a role in the findings. The negative effects of heat were more pronounced for children living in urban areas compared to rural ones. This aligns with the “urban heat island” effect, where cities trap and retain heat more than open countryside.

Access to basic services proved to be a major factor as well. Children living in households without access to improved water sources and sanitation suffered greater developmental losses when exposed to heat. Water access is essential for hydration and cooling, while sanitation prevents disease, which spreads more easily in hot conditions.

The researchers also conducted exploratory analyses regarding prenatal exposure. They looked at temperature data corresponding to the time the children were in utero. The results suggested some negative associations between heat during the third trimester and developmental outcomes, though the pattern was less consistent than postnatal exposure.

“The stronger effects among younger children and those in more vulnerable contexts were particularly striking,” Cuartas said.

There are some potential misinterpretations to avoid when considering these findings. It would be incorrect to assume that children in naturally hot regions are inherently less developed than those in cooler regions. The study design specifically controlled for regional differences to avoid this conclusion.

“Our study does not compare regions, but rather children from the same areas who happened to be exposed to different temperatures at different times,” Cuartas explained. “Heat exposure does not determine a child’s future, and many children are resilient, but it adds an avoidable risk that can compound existing inequalities, making prevention and adaptation especially important.”

As with all research, the study also has some limitations. The primary measure of development was parent-reported. Caregivers may not always assess their children’s skills with perfect accuracy. This introduces a degree of measurement error that could affect the precision of the estimates.

Another limitation is the assumption of residential stability. The researchers assigned temperature exposure based on where the child lived at the time of the survey. They assumed the child had lived in that same cluster since birth, which may not be true for families who migrated.

“Our next steps are to better understand the mechanisms linking heat to development and to identify which policies or family-level interventions can buffer children from these effects,” Cuartas said. “We are especially interested in solutions that are feasible in low-resource settings.”

The study, “Ambient heat and early childhood development: a cross-national analysis,” was authored by Jorge Cuartas, Lenin H. Balza, Andrés Camacho, and Nicolás Gómez-Parra.