EXPLAINER: Can extreme heat affect your mental health?

How heat affects the brain and body

According to adult neurologist Dr. Maxine Ty, when the body experiences extreme heat, thermoregulation begins to take place.

"It diverts blood to the skin to cool down, and we lose fluids through sweating. Even mild dehydration can already affect the brain—causing headaches, brain fog, slower thinking, and poor concentration and attention," she said.

"Higher temperature also means metabolism increases, and brain metabolic demand increases as well," she added.

Through heat and dehydration, the body is put under stress, which could then influence the chemicals and hormones that regulate our mood. 

"Our brain, specifically a part of it called the hypothalamus, also constantly monitors and manages temperature, fluid balance, heart rate, and blood pressure in response to these changes. Heat as a stressor then makes the brain work harder just to regulate temperature," Ty explained.

"We don't have the whole picture yet as to why we get anxious or irritable, but one possible explanation is that when the brain is tired and dehydrated, emotional control drops, which may explain why people feel more irritable, anxious, and less focused during hot weather," she continued.

Psychologist and mental health expert Alexandria Blake Real, meanwhile, added that heat triggers physiological responses such as elevated heart rate, increased stress hormone called cortisol, and even dehydration, all of which raise anxiety and lower stress tolerance.

"In many ways, heat-induced stress can also intersect with behavioral changes leading to emotional changes. For example, because of heat-induced stress, a person may experience sleep disruption, which also leads to irritability and emotional volatility," she said.

Who are most likely affected by the heat?

Prolonged exposure to extreme heat may also contribute to mood changes similar to those seen in Seasonal Affective Disorder, which is linked to seasonal shifts.

"While winter-pattern SAD with low mood and lethargy is most studied, a summer-pattern exists with signs like insomnia, irritability, anxiety, poor appetite, and agitation. In the Philippines, SAD is more commonly associated with the rainy season and reduced sunlight," Real said.

"Because the Philippines is highly vulnerable to climate change and extreme heat, it's important that depressive symptoms during summer be assessed carefully rather than attributed solely to the season," she added.

Heat does not affect everyone equally, and this is where environmental justice comes in.

Real noted that people with pre-existing mental health conditions, children, older adults, pregnant people, and those with chronic illness are physiologically more vulnerable to heat, yet they are often the same groups with the least access to cooling resources like air conditioning, shaded green spaces, or energy-secure housing.

"Low-income communities face compounded risk: They live in hotter urban heat islands due to dense concrete and lack of trees, work outdoors or in poorly ventilated spaces, and often can’t afford higher electricity bills during tag-init. This creates a 'thermal injustice' loop—the people most harmed by heat biologically are also the least equipped to adapt, while wealthier areas stay cooler through infrastructure and energy use that further warms the city overall," she said.

According to her, heat is both a direct cause of distress in the general population and a threat multiplier for people with existing mental health issues. 

How to manage mood swings during hot weather

To help cope with the effects of extreme heat, Ty underscored that it's important to address the underlying cause.

"Some strategies include drinking water and avoiding drinks that can worsen dehydration, such as alcohol and excessive caffeine. Cool showers, fans, and air-conditioning help as well," she said.

You can also practice what Real calls the "heat pause rule," which is being aware of how you feel, especially when negative feelings are present, and start to step away for 60 seconds.

"Within that, you can try to splash face, soak your feet, and/or drink water," she said.

Be warned, however, that too much exposure to heat can potentially be dangerous for the brain and could require treatment.

"There’s a spectrum. Early signs include headache, dizziness, and fatigue. But once a person develops confusion, unusual behavior, fainting, seizures, or loss of consciousness, that may already be heat stroke, which is a medical emergency and needs immediate treatment," Ty stressed.

To truly address the negative effect of extreme heat on one's mental health, Real highlighted that policy changes should be made by the government, such as building shaded walkways, public cooling centers, and urban trees.