As taken from YSPH student spotlight: https://ysph.yale.edu/news-article/student-spotlight–lyndsay-gavin/

As global temperatures continue to rise and heat waves are predicted to become more frequent, it is important for public health planners to understand how mental health outcomes may be impacted.

Working with the Office of Environmental Health Hazard Assessment in the California EPA, Lyndsay Gavin examined the association between temperature and mental health-related outcomes in California for both her MPH internship and thesis project.

“The physical health impacts of high temperatures have been well established — people get dehydrated or might experience heat stroke,” says, Lyndsay, “but there haven’t been very many studies looking at how climate factors can impact mental health and what the implications may be for patients with chronic mental disorders, their care facilities, and planning resources. We’re seeing more frequent heat waves and need to make sure we consider what that means for patient populations.”

Using counts of emergency room (ER) visits attributed to a mental health disorder, suicide or self-inflicted injury, and homicide or injury purposely inflicted by others between 2005 and 2013, she found that seasonally warm temperatures were associated with a 6-9 percent higher incidence of mental disorder ER visits in the warm season (May – October) and a 7-11 percent higher incidence in the cool season (November – April).

Additionally, warm temperatures were associated with a 24-29 percent higher incidence of homicide/inflicted injury ER visits in the warm season and an 11-34 percent higher incidence in the cool season.

Possible explanations for this phenomenon is exacerbation of stress, irritability and psychological distress during heat waves, impaired thermoregulation in medication use and dehydration.

The full study in its peer-reviewed published form can be accessed through PubMed.