New levels of heat may cause between 9,000 to 40,000 more suicides in the US and Mexico
According to a new study, by 2050 the rising temperatures resulting from global warming could lead to thousands of more suicides in the United States and Mexico. Researchers from the United States, Canada and Chile have analyzed temperature and suicide data for several decades in thousands of US counties and Mexican municipalities.
There is increasing evidence that climate affects human health in many ways. The links between climate and mental health are often theorized but remain poorly quantified. In particular, it is not known whether suicide rates, one of the main causes of death globally, are systematically influenced by climatic conditions. Understanding whether or not the suicide rate is related to climatic variations is important because suicide alone causes more deaths globally than all forms of violence and is among the top 15 causes of death worldwide.
A recent study has tried to find a link between climate and mental health. The research team has recognized that suicides have tended to increase for centuries during the warmer months. But since temperature is not the only factor that varies seasonally (unemployment rates or the amount of daylight, for example, also vary), the first step was to isolate the temperature from other risk factors, in order to quantify its importance.
In addition to comparing temperature and suicide data in thousands of U.S. counties and Mexican municipalities over several decades, scholars have also analyzed the language used on social media. For example, they analyzed whether, in warmer periods, the many social media posts tend to contain a higher frequency of terms such as "loneliness", "trap" or "suicide". The study shows that suicide rates increase by 0.7% in U.S. counties and 2.1% in Mexican municipalities for a 1°C increase in average monthly temperature. This effect is similar in warmer regions compared to colder ones and has not diminished over time, indicating limited historical adaptation. The analysis of depressive language in more than 600 million social media updates also suggests that mental well-being deteriorates during warmer periods.
To understand how future climate change could affect suicide rates, the team used projections from global climate models. They calculate that specific current projected temperature increases by 2050 could raise suicide rates by 1.4% in the US and 2.3% in Mexico. These effects are as large as the influence and impact of periods of economic hardship in the societies studied.
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Burke M, González F, Baylis P, Heft-Neal S, Baysan C, Basu S, Hsiang S. Higher temperatures increase suicide rates in the United States and Mexico. Nature Climate Change, 2018; DOI: 10.1038/s41558-018-0222-x