Higher-than-average monthly temperatures may be associated with small declines in mental wellbeing and small increases in suicide rates in the United States and Mexico, reports research published online this week in Nature Climate Change.

Marshall Burke and colleagues combined county-level (US) or municipality-level (Mexico) suicide data with gridded daily and monthly temperatures. They find that 1 °C increases in average monthly temperatures are associated with increases in the monthly suicide rate by 0.68% in the US (1968-2004), and 2.1% in Mexico (1990-2010). Applying a similar analysis to over 600 million geocoded social media updates from the US (2014-2015), the authors find that higher monthly temperatures were also associated with an increased use of depressive language on Twitter.

The impacts of climate change on mental health are a growing concern. This study provides longitudinal and country-scale evidence for an association between temperature and suicide, one that is consistent across geographic and socioeconomic contexts. These results cannot be used to explain individual instances of suicide, and the small size of the effect indicates that there are other, more important factors influencing aggregate suicide rates. These results do suggest a link between exposure to higher temperatures and declines in mental wellbeing; however, one that, under unmitigated climate change, could lead to between 9,000 and 44,000 additional suicides across the US and Mexico by 2050. The authors conclude that these results add further impetus to better understand why temperature affects suicide and to implement policies to mitigate future temperature rise.