Suicide rates are likely to increase as the earth gets warmer, according to a new study published in the journal Nature Climate Change. The findings suggest that projected temperature increases through 2050 could lead to an additional 21,000 suicides in the United States and Mexico.
“We’ve been studying the effects of warming on conflict and violence for years, finding that people fight more when it’s hot,” said Dr. Solomon Hsiang, study co-author and associate professor at the University of California, Berkeley. “Now we see that in addition to hurting others, some individuals hurt themselves. It appears that heat profoundly affects the human mind and how we decide to inflict harm.”
But beyond the heat, there are many other factors that also vary seasonally such as unemployment rates or the amount of daylight, and until now it has been difficult to determine the role of temperature apart from other risk factors.
To separate the role of temperature from other contributing issues, the research team compared historical temperature and suicide data across thousands of U.S. counties and Mexican municipalities over several decades.
They also observed the language in over a half-billion Twitter updates or tweets to further determine whether hotter temperatures impact mental well-being. They analyzed, for example, whether tweets contain language such as “lonely,” “trapped” or “suicidal” more often during hot spells.
The findings give strong evidence that hotter weather increases both suicide rates and the use of depressive language on social media.
“Surprisingly, these effects differ very little based on how rich populations are or if they are used to warm weather,” said researcher Dr. Marshall Burke, assistant professor of Earth system science in the School of Earth, Energy & Environmental Sciences at Stanford University.
For example, the effects in Texas are some of the highest in the country. Suicide rates have not declined over recent decades, even with the introduction and wide adaptation of air conditioning. If anything, the researchers say, the effect has grown stronger over time.
To help determine how future climate change might affect suicide rates, the researchers used projections from global climate models. Their findings show that temperature increases by 2050 could increase suicide rates by 1.4 percent in the U.S. and 2.3 percent in Mexico.
These effects are approximately as large as those of economic recessions (which also increase the rate) or suicide prevention programs and gun restriction laws (which decrease the rate).
“When talking about climate change, it’s often easy to think in abstractions. But the thousands of additional suicides that are likely to occur as a result of unmitigated climate change are not just a number, they represent tragic losses for families across the country,” said Burke.
“Suicide is one of the leading causes of death globally, and suicide rates in the U.S. have risen dramatically over the last 15 years. So better understanding the causes of suicide is a public health priority.”
Still, the researchers emphasize that rising temperatures and climate change should not be seen as direct motivations for suicide. Instead, they point out that temperature and climate may increase the risk of suicide by affecting the likelihood that an individual situation leads to an attempt at self-harm.
“Hotter temperatures are clearly not the only, nor the most important, risk factor for suicide,” Burke said. “But our findings suggest that warming can have a surprisingly large impact on suicide risk, and this matters for both our understanding of mental health as well as for what we should expect as temperatures continue to warm.”
Source: Stanford University