High Temperatures Worsen Range of Mental Health Outcomes, Study Finds

High ambient temperatures have a range of mental health effects, including an increased risk of suicide, and an increase in heat-related morbidity and mortality among people with known mental health problems, a recent study has found.

Published last month in the journal Public Health during the hottest summer on record in much of the world, it is the largest study of its kind to provide an association between mental health outcomes and heat waves and may have wide ranging implications for the public health community.

Researchers conducted a systematic review of 35 pre-existing studies that examined the link between high ambient temperatures and a range of mental health conditions including suicide, bipolar disorder, depression, schizophrenia, dementia, and substance misuse.

As well as an association between high temperatures and suicide, researchers also found a significant increase in mental health related admissions and emergency department visits during periods of high heat. The researchers behind the study recommend that mental health impacts should be incorporated into plans for the public health response to heat waves and high temperatures.

Study lead and Environmental Public Health Scientist at Public Health England, Ross Thompson, believes that as evidence evolves, temperature thresholds that account for other risks could be incorporated into hot-weather warning systems.

“All-cause mortality is generally the only outcome measure used to determine temperature thresholds for action during periods of high temperature, yet we know that morbidity, including psychological morbidity, also increases as temperatures rise.

Developing the evidence base to understand the temperatures at which morbidity is negatively impacted can inform the public health response to heatwaves and high temperatures. This may also benefit healthcare providers when developing and implementing organisational response plans, allowing them to plan for and respond to increased demand.”

One of the studies included in the review found that an increase in temperature or humidity by just one unit (1°C, or 1hPa respectively), led to a significant increase in the proportion of the population over 45 years of age in Australia accessing treatment with symptoms of extreme psychological distress. A different study found that the risk of mortality among individuals who had already been diagnosed with schizophrenia more than doubled on heat wave days.

The evidence comes as many countries around the world have been affected by severe heatwaves, leaving thousands dead and tens of thousands more suffering from heat-related illnesses. It also joins an expanding body of evidence which is beginning to conclusively prove the wide-ranging, and often surprising health impacts of high temperatures and heatwaves which will significantly worsen under predictions of climate change and global warming.

Useful links:

Associations between high ambient temperatures and heat waves with mental health outcomes: a systematic review

https://www.ncbi.nlm.nih.gov/pubmed/30007545

The Importance of Humidity in the Relationship between Heat and Population Mental Health: Evidence from Australia

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0164190

The Effect of Heat Waves on Mental Health in a Temperate Australian City

https://ehp.niehs.nih.gov/doi/10.1289/ehp.11339