Increased average monthly temperatures may be linked to a modest rise in adverse mental health issues, according to a study published in Proceedings of the National Academy of Sciences of the United States of America.
Here are five things to know:
1. For the study, Nick Obradovich, PhD, lead author and researcher at the Massachusetts Institute of Technology's Media Lab in Cambridge, and his colleagues examined data from the CDC's Behavioral Risk Factor Surveillance System, which comprises self-reported personal mental health data on about 2 million randomly sampled U.S. residents. Researchers also examined daily meteorological data from 2002-12.
"We gathered about a decade's worth of data from this survey, which is about 2 million people responding to the same question. The question basically asks: How, over the recent period, has your mental health status been?" Dr. Obradovich told CNN.
2. Researchers matched these responses to meteorological data from each survey respondent's city, creating a "decade's worth of information about how environmental conditions related to the way people reported their mental health status," Dr. Obradovich told CNN.
3. Researchers analyzed this information by comparing: three ways.
- Temperatures and precipitation over a 30-day period to mental health
- Long-term warming trends to mental health reports in individual cities
- Mental health reports from people affected by Hurricane Katrina to reports from people not affected by the storm
4. Researchers found an increase in average monthly temperature from 25 to 30 degrees Celsius to greater than 30 degrees Celsius was linked to a 0.5 percentage point increase in the risk of mental health difficulties. If this temperature change were generalized across the nation, about 2 million additional individuals would report mental health difficulties, according to Dr. Obradovich.
5. The prevalence of mental health problems was four percentage points higher for people affected by Hurricane Katrina. Overall, individuals with lower incomes, people with existing mental health problems and women were most vulnerable to climate change.
"We don't exactly know why we see high temperatures or increasing temperatures produce mental health problems," Dr. Obradovich told CNN. "For example, is poor sleep due to hot temperatures the thing that produces mental health problems? We have a lot of work to do to figure out precisely what is causing what."