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UAlbany study finds exposure to heat, humidity and the sun can trigger mental disorders

A graphic depicting the findings of the study that exposure to high heat, humidity and sun radiation can trigger mental disorders.
Study authors Xinlei Deng, Jerald Brotzge, Melissa Tracy, Howard H Chang, Xiaobo Romeiko, Wangjian Zhang, Ian Ryan, Fangqun Yu, Yanji Qu, Gan Luo, Shao Lin

A recent study led by researchers at the University at Albany finds that exposure to sustained sunny, hot and humid weather can trigger and increase symptoms of mental health disorders. The study compared data from the New York State Mesonet – a network of weather stations across the state – with hospital emergency visits.

WAMC's Jim Levulis spoke with Shao Lin, the study’s senior author and a professor at UAlbany’s School of Public Health.

Lin: This is probably the first study in the nation to look at the multiple factors of mental health problems. So the major findings, the first thing is we found that sun radiation and relative humidity showed the highest increase for mental health risk. And the second finding, we found temperature had a sharp effect. And heat index also seemed to increase the risk, but the risk is long, it lasts a whole week long. And we also found the rainfall duration had an inverse effect, just like the longer duration. And another important finding is we found sun radiation, relative humidity, high temperature and heat index, the effects also show up in September and October, so it's out of summer. So we call them transitional month effects. And those effects show up for all these weather factors. And we also found the joint effect among sun radiation, relative humidity, and high temperature, had the highest risk of mental health problems. Finally, we found some of the subtypes of mental health problems, such as psychoactive substance use and also mood disorder, and adult behavior disorders had a significant increase after the heat exposure.

Levulis: Do we know why this sustained heat, sustained humidity, sustained high levels of sun radiation cause this type of response across these disorders?

Lin: Yeah, I think it's biological. So as we indicate in our paper, it’s like the hormones change because the heat can change people’s hormone levels like dopamine, and also some other hormonal change, which also affect the people's reaction to heat. So that can cause the mental health problems.

Levulis: How might health care, government and public safety leaders use these findings?

Lin: Yeah, I think that's a very good point. The first thing I want to tell the government and the healthcare workers is we should look at all the weather factors’ joint effect. Not temperature alone. So we look at sun radiation and humidity because there are joint effects between the highest sun radiation, the highest humidity and also temperature is the strongest. So it's much stronger with the joint effect effects than the single weather effect. So on those days when all these things are very high, I think that the healthcare workers or the doctors, all the other policymakers are thinking about public and mental health patients and should be paying more attention to because they saw the highest risk.

Another thing is those effects, don’t just show up in a typical summer. We also found that the effects show up in the transitional months of September and October. Especially some of the weather effects for sun radiation and humidity are stronger in September than in the typical summer which implied the warning outside of summer is very important. So right we are only doing warnings in the typical summer, not in a transitional month. So we encourage policymakers to do the early warning, or the late warning after the summer weather. The third important thing is that we identify the thresholds for each of these risk factors in our paper, which will be important for the policymaker like a health department to use these thresholds. So when the temperature or humidity or sun radiation reach the threshold we should expect an increased risk for mental health episodes.

Levulis: And my final question, you know, I'm not sure if there was a look at this, but I know, your study found that there was an associated increase in some forms of violence when temperatures were at their highest. Might this partially explain why there tends to be more violence? Such as, you know, instances like shootings in the summer months?

Lin: Yeah, we typically find, like substance abuse and the some of the violence increase in the summer months due to the extreme weather. So we don't know that the reason, but probably this will be related to some other the hormonal change and also maybe the people are not in a stable status. They feel really stressful because of the temperature. So because we don't do the laboratory, like an animal study, we don't know the exact mechanism for that, but that's what we found. So we think about based on the animal study within this space, probably the biological reason based on the hormonal change and the mood change, because we also found that mood disorder is significantly increased after the June weather.

Jim is WAMC’s Associate News Director and hosts WAMC's flagship news programs: Midday Magazine, Northeast Report and Northeast Report Late Edition. Email: jlevulis@wamc.org