How does weather affect human mental health?

Credit: Shutterstock Hurricane Harvey is now the largest rainfall event in US history. According to the Centers for Disease Control and Prevention (CDC), nearly 50% of homes in Houston are flooded and over 30,000 people in the Greater Houston area are in emergency shelters. Hundreds of thousands more are seeking higher ground. Thousands have been rescued by volunteer organizations and by the US Coast Guard, but thousands more are expected to be left stranded.

What is the effect of weather on mental health? How are extreme weather events – floods, droughts, hurricanes, tornadoes – and related extreme weather, including wildfires, storms, and the like, affecting people's mental health? What are the mental health impacts of climate change? What is the impact of extreme weather on mental health in other parts of the world?

These are important questions, and fortunately, there are a few studies on the topic.

Getting into the weeds

For the purposes of our discussion, we'll assume that disasters are associated with mental health issues. We will also use the term "disasters" broadly to include the wide range of extreme events that can affect human health, including floods, fires, earthquakes, and the rest of the variety of natural hazards that can occur around the globe.

So what do studies on natural disasters and mental health tell us about how climate change is influencing people's stress and anxiety? One study that looked at the mental health impacts of natural disasters, particularly flooding, found that these types of disasters are associated with higher rates of anxiety and depression.

Another study showed a strong association between hurricane anxiety and overall anxiety. Similar results were found with wildfires, especially among individuals who are more vulnerable.

How much anxiety and depression do hurricanes and wildfires increase? In the case of hurricanes, researchers found an increase in anxiety and depression symptoms in adults older than 45, while those in the younger, who are more vulnerable to mental health problems, had only a small increase in depression. The associations were stronger in people who experienced chronic conditions.

Heat waves and more

Mental health issues can also be exacerbated by heat waves. In August 2012, a heat wave broke across the southeastern part of the United States. People experienced increased mental health problems, including depression and anxiety, because of the heat and humidity.

A different set of researchers investigated the mental health effects of one of the world's worst heat waves, which occurred in 2003 in Europe. They found that the heat waves were associated with increased mental health problems, including insomnia, dizziness, and anxiety. These mental health effects were the strongest in adolescents.

People have also been disturbed by the images from Texas and Louisiana of the chaos caused by floodwater.

A study published in 2010 looked at the mental health effects of the Great Flood of 1993 in North Carolina. That flood was associated

Mental health practitioners are busy responding to the flood of callers at Houston Mental Health Services, where they treat adults. At the shelter in downtown Houston, mental health workers said many of their clients are struggling with a wide range of psychological issues - from anxiety to post-traumatic stress disorder. They also worry about an uptick in cases of children displaying extreme anxiety or obsessive-compulsive disorder.

Wildfire mental health

Another study looked at the mental health impact of wildfires in southern California, which is an area prone to the risk of fire. A significant number of people evacuated, and many of those evacuees had returned home by May.

As a result, they found a strong association between the psychological symptoms of post-traumatic stress and the effects of wildfire on mental health. They also found that those who went through the ordeal had greater anxiety and depression compared with those who did not.

Mental health issues can have negative consequences on other aspects of life, too, including work productivity and physical health.

There's also some evidence that people who experience post-traumatic stress are more likely to die in a future natural disaster, because of an increased risk of dying of dehydration, which is common during and after a disaster.

Climate change impact

There are several ways that climate change can exacerbate mental health problems. One is by increasing the risks of physical health problems. For example, rates of mental health problems are higher in areas with higher rates of asthma, which is a symptom of chronic air pollution.