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Paper: Surprising Effects Occur After Just a Few Warm Days — Even at 70°F
In a nutshell
- Higher temperatures (even moderate ones between 64-78°F) can temporarily reduce connectivity in crucial brain networks in children, including those responsible for emotion regulation.
- Changes in the salience network, which helps process emotions, may help explain why heat waves correlate with increased mental health emergencies in young people.
- Simple measures like ensuring children stay hydrated, get adequate sleep, and have access to cool environments during hot weather may help protect developing brains.
ROTTERDAM, Netherlands — Rising global temperatures aren’t just changing our planet—they may be altering the developing brains of our children, suggests new research from the Netherlands. Scientists have discovered that exposure to high ambient temperatures affects brain functioning in preadolescents, potentially explaining why heat waves correlate with increased mental health emergencies among young people.
In 2024, Earth experienced its warmest year on record, with global temperatures projected to exceed 1.5°C above pre-industrial levels within five years. As climate change intensifies, understanding its effects on human health becomes increasingly urgent, particularly for vulnerable populations like children.
The Impact of Heat on Young Brains
Until now, we’ve known that extreme temperatures correlate with acute mental health events in young populations—emergency room visits increase during heat waves for conditions ranging from adjustment disorders to anxiety and self-harm. What we haven’t understood is why. This study provides the first neurobiological evidence of how temperature directly affects brain function in children.
A team from the Generation R Study in Rotterdam examined 2,229 children aged 9-12 years, revealing that higher temperatures during the week before brain imaging was linked to decreased connectivity in key brain networks. These findings offer the first neurobiological evidence of how temperature directly affects brain function in children.
Brain scans showed that heat exposure specifically affected three crucial brain networks:
- The medial parietal network, which helps integrate information about our body and surrounding space, enhancing self-awareness and perspective-taking.
- The salience network, which detects important stimuli and helps regulate emotions. Research has linked lower connectivity in this network with increased suicidal ideation in adolescents with depression.
- The hippocampus, essential for learning and memory, which also helps the body respond to stressors and regulates stress response systems.
The temperature effect was strongest the day before the brain scan and gradually decreased over preceding days, indicating a relatively immediate but temporary impact of heat exposure.
Climate Change and Mental Health
Particularly concerning was the consistent effect across both cold and warm seasons, indicating that both absolute high temperatures and unseasonably high temperatures affect the brain. This aligns with previous findings on temperature and acute mental health events.
The findings regarding the salience network raise particular concerns given its established connection to suicidal thoughts. The researchers propose that decreased functional connectivity within this network might partially explain the association between high temperatures and suicide rates documented in earlier studies.
Several mechanisms could explain these results. Dehydration is one possibility—children lose fluids more quickly than adults when exposed to heat. Sleep disruption from high nighttime temperatures could also play a role, as sleep deprivation affects connectivity in the salience network.
Protecting Young Minds in a Warming World
From a public health perspective, these findings, published in the Journal of the American Academy of Child & Adolescent Psychiatry, highlight the importance of protecting children from excessive heat. As summers grow hotter and heat waves become more frequent, improved access to cooling resources, energy assistance programs, and increased green spaces may become crucial for protecting cognitive and emotional well-being.
For parents and educators, the research suggests paying closer attention to children during hot weather. Ensuring proper hydration, adequate sleep, and access to cool environments may help mitigate these neurological effects.
The brain changes observed occurred at temperatures that many would consider warm but not extreme—daily mean temperatures between approximately 64°F to 78°F. This indicates that even moderate heat can affect brain function in developing minds.
As the researchers note, public health policies aimed at protecting children from high temperatures may reduce their potential impacts on brain function. This study makes visible what was previously hidden: the ways our warming world might be changing the very architecture of developing brains.
Paper Summary
Methodology
This research took place within the Generation R Study, a population-based birth cohort in Rotterdam, Netherlands, that follows children from pregnancy onward. The study focused on 2,229 children between ages 9 and 12 who underwent brain MRI assessments. Researchers obtained daily mean temperature estimates at each participant’s residential address using a high-resolution urban climate model called UrbClim, which provides temperature data at a horizontal resolution of 100 meters. The model incorporates various data sources including land cover, soil sealing, vegetation maps, and meteorological data. Temperature values were assigned to each participant for the seven days preceding their MRI scan, a timeframe chosen based on previous research examining temperature effects on acute mental health events. To ensure accuracy, the researchers validated their model against observed temperature data from local monitoring stations, achieving an R² of 0.971 (indicating very high accuracy).
The brain scans were conducted using a 3.0T MRI scanner, with children instructed to stay awake with their eyes closed during the resting-state functional MRI. The researchers used standardized software to preprocess the brain imaging data and calculated functional connectivity based on a parcellation that defines 333 cortical regions grouped into 13 resting-state networks, plus two additional subcortical regions (the hippocampus and amygdala). Within-network connectivity was defined as the average correlation among all regions within each network, while between-network connectivity measured the average correlation between regions of different networks. To account for potential confounding variables, the researchers collected extensive socioeconomic and demographic information and used statistical techniques to adjust for these factors in their analysis.
Results
After analyzing the relationship between temperature exposure and brain connectivity, the researchers found that higher daily mean temperatures during the week before the MRI assessment were associated with lower within-network connectivity in several networks. After applying statistical corrections for multiple comparisons, three associations remained significant: the medial parietal network, the salience network, and the hippocampus.
For the medial parietal network, daily mean temperatures between 17.7°C and 23.8°C over a 7-day period were associated with lower functional connectivity. For the salience network, temperatures between 18.4°C and 25.5°C showed the same effect. For the hippocampus, temperatures between 20.4°C and 23.0°C were linked to decreased connectivity. In all three cases, the effect was strongest the day before the MRI scan and gradually decreased for days further back in time.
Both daily minimum and maximum temperatures showed similar patterns, with slightly stronger effects for maximum temperatures. The associations were consistent across different seasons, suggesting that both absolute high temperatures and unseasonably high temperatures can affect brain connectivity. No significant effects were found for lower temperatures, and no between-network connectivity associations remained significant after statistical corrections.
Limitations
The researchers acknowledge several limitations of their study. First, they only had temperature estimates from participants’ homes, not from schools or other locations where children might spend significant time. This could lead to some inaccuracy in measuring actual temperature exposure. They also lacked data on indoor temperatures, which could be particularly important in the Dutch context where heating is more common than air conditioning.
Another limitation was the potential for misclassification since they couldn’t confirm that children were at their residential addresses during the 7 days preceding the MRI. Additionally, there are no established thresholds for what constitutes “normal” versus “abnormal” functional connectivity values, making clinical interpretation challenging.
The parcellation scheme used to define brain regions was developed based on adult brains, which might not perfectly align with children’s brain architecture. Finally, while the researchers used statistical techniques to mitigate selection bias and adjusted for many confounding variables, they couldn’t rule out residual confounding from unmeasured factors.
Funding and Disclosures
The study was supported by various funding sources, including the Erasmus Medical Center, Rotterdam; the Erasmus University Rotterdam; the Netherlands Organisation for Health Research and Development; the Netherlands Organisation for Scientific Research; and the Ministry of Health, Welfare and Sport. Temperature estimations were funded by the Spanish Institute of Health Carlos III. Several researchers received individual fellowships and grants from organizations including the Spanish Institute of Health Carlos III, the Agencia Estatal de Investigación, and the European Social Fund. The authors reported no conflicts of interest.
Publication Information
This research paper titled “Exposure to Ambient Temperature and Functional Connectivity of Brain Resting-State Networks in Preadolescents” was published in the Journal of the American Academy of Child & Adolescent Psychiatry on January 27, 2025. The lead author is Laura Granés, MD, along with an international team of researchers from institutions in Spain and the Netherlands.
