An increase in average monthly temperatures of just 1掳C seems enough to increase suicide rates. Analysis of data from the US and Mexico suggests that if climate change continues unchecked, rising temperatures could lead to thousands more suicides in these countries by 2050.
Marshall Burke at Stanford University in California and his colleagues analysed public health data on more than 850,000 suicides over 36 years in the US and more than 611,000 suicides over 20 years in Mexico. For each degree of average monthly temperature increase, they found that suicide rates rose by an average of 0.7 per cent in the US, and 2.1 per cent in Mexico.
鈥淲hether you鈥檙e in a really cold place to start with or a really hot place, you鈥檙e going to see suicide rates increase as temperatures do,鈥� Burke says. 鈥淚f you heat up a January, you have the same effect as if you heat up a June. That鈥檚 why this is so surprising.鈥�
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Burke and his team used census data to account for gender, income and geography and found no difference for any factor. They also accounted for the adoption of air conditioning in each US county or Mexican municipality and found that it had no effect.
Climate change
Burke suggests that serotonin, a brain chemical known to affect mental health and regulate body temperature, could be behind the increase. The team predicts that climate change could lead to 40,000 additional suicides in the US and Mexico by 2050.
Grady Dixon at Fort Hays State University in Kansas thinks this prediction of 40,000 may be too high. The trend so far suggests we will get used to higher monthly temperatures, but that with each increase, suicides will go up again, he says. 鈥淚n the future, we鈥檒l still have the same suicide rate 鈥� but that鈥檚 still not a good thing.鈥�
If higher temperatures affect the brain or body, other problems may rise in line with climate change. When Burke鈥檚 team analysed more than 620 million tweets from US Twitter users, they found that depressive language became more common when temperatures were higher than normal.
鈥淭his is evidence that the health burden of climate change is going to be much larger than we thought,鈥� Burke says.
Nature Climate Change
Read more: The fading American dream may be behind rise in US suicides
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