Interpersonal and Self-Inflicted Violence Linked to Temperature Spikes

Warming temperatures are connected to increases in violence-related hospital visits—including both interpersonal and self-inflicted violence—according to a new analysis of 14 years of Medicaid claims data. The study is led by researchers at Columbia University Mailman School of Public Health. The findings are published in the journal Communications Sustainability.

The researchers analyzed 332,293 Medicaid claims for interpersonal and self-inflicted violence-related hospital visits in the United States. They compared daily hospital visits with local temperature patterns over the following six days. They found that as temperatures rose, violence-related hospital visits also increased, especially in the first two days after higher heat stress. A 5°C increase was associated with a 1.5 percent increase in interpersonal and a 3.7 percent increase in self-inflicted violence visits.

The new findings are in line with other research on the increase in violent deaths, including assaults and suicides, during warm months. Warmer temperatures and increased outdoor time correlate with more frequent face-to-face interactions, contributing to a rise in arguments, confrontations, and assaults. Higher temperatures also increase outbursts of temper and more negative reactions to others, particularly when there is access to firearms. Reduced quality and length of sleep from higher temperatures can also result in more irritable individuals during the daytime, particularly in low-income homes where air conditioning is less prevalent. Increased hospital visits and consumption of alcohol and drugs during higher temperatures may also influence violent behavior toward others and oneself. 

“Our results emphasize the importance of integrating mental health into climate change preparedness,” says the study’s first author, Robbie M. Parks, PhD, assistant professor of environmental health sciences. “For example, messaging about the risks of violence during warmer weather would be warranted.”

Low-income individuals who qualify for Medicaid are also likely to be most impacted by the heat due to a lack of home air conditioning. They also have limited access to regular preventative health care, including mental health care.

“Equitable distribution of home air conditioning, coupled with other investments in community-based programs and adaptation strategies to mitigate the impacts of higher temperatures, can help alleviate the vulnerabilities faced by these communities and foster a safer and more resilient society overall,” Parks adds.

Additional authors include Ilan Cerna-Turoff and Jutta Lindert at Columbia Mailman; Lauren Flynn, Zifan Gu, Danielle Braun, and Francesca Dominici at Harvard T. H. Chan School of Public Health; Cascade Tuholske at Montana State University, Bozeman; and Marianthi-Anna Kioumourtzoglou at the School of Public Health, Brown University.

Funding was provided by the National Institutes of Health (grants ES033742, ES022631, ES030616, ES028805, ES028033, MD012769, AG066793, ES029950, AG060232, AG071024, ES028472, ES009089, AG093975). Funding was also provided by the Harvard Climate Change Solutions Fund.

The authors declare no competing interests.