Ambient Temperatures Linked to Psychiatric Symptoms in Youth

A new study released this week adds to mounting evidence that suggests climate change, with extreme hot and cold temperatures, threatens not only physical health but also mental well-being.

Analyzing data from two population-based birth cohorts in Europe, researchers found that ambient temperature has distinct associations with psychiatric symptoms in adolescents, with cold exposure in the Netherlands associated with more internalizing symptoms and heat exposure in Spain associated with more attention problems.

“As climate change intensifies, these associations may become more pronounced in the near future,” wrote investigators, led by Mònica Guxens, MD, with ISGlobal and Pompeu Fabra University, Barcelona, Spain.

The study was published online on January 28 in JAMA Network Open.

‘Significant and Growing Threat’

A 2023 position statement from the American Psychiatric Association (APA) noted that climate change poses a “significant and growing threat” to public health in general and to mental health in particular.

Ambient temperature extremes have been associated with physical health risks, but their influence on psychiatric symptoms in adolescents is less clear, particularly the association of ambient temperatures with psychiatric symptoms.

Guxens and colleagues assessed the relationship between ambient temperature exposure and psychiatric symptoms in 3934 adolescents in the Netherlands and 885 adolescents in Spain.

The primary outcomes were internalizing, externalizing, and attention problems measured with the maternal-reported Child Behavior Checklist for ages 6-18 years.

Daily ambient temperature 2 weeks, 1 month, and 2 months before outcome assessment was calculated between 2015 and 2022. Daily temperatures ranged from −5.2 °C to 32.6 °C in the Netherlands and 3.3 °C to 33.9 °C in Spain.

Mental Health Hit

In the Netherlands, cumulative exposure to colder temperatures (3.3 °C-12.4 °C) over 2 months was significantly associated with more internalizing problems such as anxiety and depression (eg, 0.76 higher square root points at 5.5 °C exposure over the 2-month exposure period), the researchers found.

In Spain, cumulative exposure to warmer temperatures (15.6 °C to 24.3 °C) was associated with more attention problems (eg, 1.52 higher square root points at 21.7 °C exposure over 2 months of exposure).

No significant associations between ambient temperatures and externalizing problems were observed, despite the “heat-aggression” theory that hotter temperatures are associated with violence and aggression, they pointed out.

Cold and heat exposure disrupts thermoregulation and cell function, which can lead to changes in blood pressure, inflammation, or impaired brain cooling and oxygenation. Thermal discomfort has also been shown to trigger irritability and harm mood, the study team noted.

The findings highlight “the importance of conducting further research across diverse climates to quantify the intricate and multifactorial association of climate change with mental health,” researchers wrote.

The authors identified several potential limitations to their study, including exposure misclassification and possible maternal bias in reporting child behavior.

Also, the study evaluated temperature exposure only up to 2 months prior to psychiatric assessment and longer-term effects remain unknown. The researchers lacked information on the exact timeframe of adolescents’ internalizing, externalizing, and attention problems.

Rich Dataset, Interpretation Tough

Reached for comment, Susan Clayton, PhD, professor and chair of Psychology, The College of Wooster in Wooster, Ohio, told Medscape Medical News the study is “novel in the rigorous methods they used and also in considering impacts of cold as well as heat; a lot of studies only look at heat.”

Clayton, who wasn’t involved in the study, noted that climate change can have mental health impacts for many reasons — two in particular with regard to this study.

“Heat can have inflammatory effects on the brain. It also can decrease sleep quality and increase intergroup and interpersonal conflict and aggressive tendencies in general,” Clayton said.

“Experiences of climate change are associated with increased worry and anxiety, which we know to be associated with anxiety and depression, though it doesn’t automatically lead to mental health problems,” she added.

Also weighing in on the study, Joshua Wortzel, MD, chair of the APA Committee on Climate Change and Mental Health, told Medscape Medical News that it’s “novel to have these kinds of rich datasets (both mental health measures and temperature data) with large sample sizes. However, interpreting these data are difficult.”

“For example, we know that individuals with mental illness are affected differently by temperature than healthy controls,” explained Wortzel, adjunct assistant professor, Yale University Department of Psychiatry, New Haven, Connecticut.

He noted that a recent ecological study in Switzerland looking at the effects of ambient temperature on mood showed warmer temperatures improved mood in healthy individuals but were associated with worse mood outcomes in individuals diagnosed with depression, anxiety, and schizophrenia.

“I did not see a clear explanation in the paper about how mental health diagnoses were accounted for in their modeling. It is also hard to know what temperatures the subjects actually experienced compared to estimates of outside temperatures at their homes. This is a critique of much/all of this literature looking at associations between temperature and mental health,” Wortzel cautioned.

While research on how ambient temperature affects mental health is needed, “Unfortunately, I personally cannot draw any large takeaways from their paper that help elucidate this field further, other than highlighting that the effects of temperature on mental health are likely different by demographic and the mental health symptoms we are trying to measure,” Wortzel said.

The study had no commercial funding. Guxens, Clayton, and Wortzel had no relevant disclosures.