Dive Brief:

• A new study published in the Proceedings of the National Academy of Sciences finds that experiencing warmer temperatures and increased precipitation are associated with more mental health issues, a warning of another possible health effect of climate change.
• The study compared almost 2 million randomly-selected responses to a Centers for Disease Control and Prevention’s (CDC) survey to climate and meteorological data. An increase in the average monthly temperature was associated with a rise in responses to a question indicating general mental health issues (not necessarily psychiatric diseases). When the average monthly maximum temperature rose from between 25-30 degrees Celsius to more than 30 degrees C, the number of responses indicating mental health trouble rose 1%, which would be the equivalent of nearly 2 million people in the U.S. 
• The study also found that exposure to tropical cyclones worsened mental health; exposure to Hurricane Katrina was associated with a 4% increase in responses indicated mental health issues.

Dive Insight:

The actual mechanism for the link between warming temperatures and mental health is still unclear. In an interview with CityLab, study author Nick Obradovich of the MIT Media Lab said it could be everything from the fact that rainy weather is unpleasant to heat making it difficult to get a full night’s sleep. General anxiety about climate change — especially in areas that seeing extreme weather events — no doubt plays a role.

There’s been increasing evidence of the impact climate change has on mental health. A study published in July, for example, found that warmer temperatures were associated with a higher suicide rate, projecting that the U.S. and Mexico could see a combined increase in suicides of between 9,000 and 40,000 by 2050 if climate change was unabated. The American Psychiatric Association in 2017 adopted a statement recognizing that "climate change poses a threat to public health, including mental health," citing studies linking climate change and increased natural disasters to "anxiety-related responses" and "chronic and severe mental health disorders.'

More study into why people’s mood seems to be changing with the climate can help governments and health care providers figure out how to combat it, although Obradovich said there could be “a variety of small-scale behavioral adaptations” that could help people cope, including tweaking sleeping habits.

As city governments work to mitigate the impacts of climate change — especially in the absence of federal intervention — the mental health implications also have to be considered. Several cities are already working on combating depression holistically by addressing problems like loneliness; further research on how climate conditions affect health will bring another angle to those efforts.