As Heat Rises, So Do Suicides, a Stanford Study Finds

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Baker's thermometer shows the temperature on July 23, 2014, after a renovation replaced its 5,000 light bulbs with LEDs. The National Weather Service has issued an excessive heat warning through Thursday for the San Fernando, San Gabriel and Ventura County Valleys. Temperatures up to 108 degrees are expected Tuesday and Wednesday. (Ethan Miller/Getty Images)

A warming climate may carry a sneaky effect on mental health. A Stanford University-led research team warns in a study published today that hotter temperatures are raising the risk of suicide.

Going back to the early 19th century, scientists, sociologists and poets all noticed more people die by suicide in spring. That’s caused other teams to investigate sunlight’s influence on mental health and the connection between allergies and suicide.

Marshall Burke, an associate professor of earth systems sciences at Stanford, worked with colleagues at UC Berkeley and an international team to amass decades of death records for the U.S. and Mexico, and localized temperature records. They found that when temperatures rose about 2 degrees Fahrenheit in a given location and given month, deaths by suicide rose by about 1 percent.

“Even a one percent effect - if multiplied across many people in the United States - implies a very large additional health burden from increasing temperature,” says Burke.

Globally, nearly 800,000 people die by suicide each year, according to the World Health Organization. Suicides in the United States and Mexico represent abut 7% of the total. In the United States, suicide is a top-ten leading cause of death, and in the most recent 17 years on record, the nation’s overall suicide rate has increased 28%, according to the National Institute of Mental Health.


Burke's newly-released study doesn’t suggest that hot temperatures cause people to harm themselves. And he stresses that suicide has other larger and well-documented risk factors. Researchers now wonder whether warmer temperatures are some sort of a biological trigger.

But based on this data and on global models, this team projects that if climate change continues unchecked until the middle of this century, hotter temperatures could cause at least 20,000 additional deaths in the two countries studied.

“That sounds like an abstract statistic,” Burke says, "but we should think of that as individuals and individual families that are going to be fundamentally affected by that if temperatures increase."

He notes that air conditioning and wealth don’t seem to mitigate the link between hotter temperatures and suicide. So as temperatures rise, he expects the risks of heat to human health will continue to rise too.