The UK is expected to experience its first heatwave of the year, with temperatures expected to reach the mid-30s, meaning the usual excitement for sunshine may be overshadowed by underlying concerns.
Beyond the immediate physical discomfort and fatigue, this intense heat is increasingly impacting our mental health and overall mood.
To understand the psychological effects of long-term high temperatures and explore strategies to maintain balance, The Independent spoke to practicing psychologist Dr Ravi Gill.
Do heat waves affect our mood?
Physiological changes in the body and brain due to heat can have a significant impact on mood during a heat wave. “Heat disrupts neurotransmitter systems (serotonin), disrupts sleep, and increases stress hormones such as cortisol, which are important regulators of mood and impulse control,” says Gill.
Psychologists say the physical discomfort and sleep disturbances caused by heatwaves can also exacerbate mood swings, causing spikes in anxiety and worsening irritability.
“Prolonged discomfort and environmental stress can strain your emotional resilience, making even the slightest stimulation feel overwhelming,” Gill adds. “Heatwaves can also increase social tensions in homes, transport, and public spaces, turning small triggers into conflicts.”
Research also suggests that people with pre-existing mental health conditions are more vulnerable during heatwaves.
“Conditions such as anxiety, depression, bipolar disorder, and schizophrenia can make it difficult to recognize the early signs of heat stress and take action. Additionally, some psychiatric medications (such as antipsychotics, certain antidepressants, and mood stabilizers) reduce the body’s ability to sweat and regulate temperature, increasing the risk of heat exhaustion and heat stroke,” notes Dr. Gill.
How does heat-related sleep disturbance affect our mood and mind?
“Higher nighttime temperatures make it harder for your core body temperature to cool down, which is essential for initiating and maintaining deep, restorative sleep,” says Gill. “People wake up frequently, especially during REM sleep, which is essential for emotional processing and memory consolidation. Difficulty falling and staying asleep reduces overall rest.”
This can have a huge impact on our emotional control.
“Sleep deprivation reduces activity in the prefrontal cortex (which is responsible for impulse control) and increases reactivity in the amygdala (associated with fear, anger, and anxiety), which makes us more emotionally unstable,” Gill explains. “Lack of REM sleep amplifies stress responses and reduces resilience to everyday frustrations.
“Furthermore, sleep deprivation impairs attention, working memory, decision-making and problem-solving skills, and increases mental fatigue.”
How can heatwaves affect cognitive functions such as memory, concentration, and decision-making?
“Heatwaves can affect and impair core cognitive functions such as memory, concentration and decision-making, due to a combination of direct effects on the brain and secondary factors such as dehydration and sleep disturbances,” Gill says.
Reduced cerebral blood flow, neurotransmitter disruption, and electrolyte imbalance are just some of the factors that can significantly impact our cognitive function during heat waves.
“Higher temperatures cause blood vessels to dilate, diverting blood to the skin for cooling, and can reduce blood flow and oxygen supply to the thinking centers of the brain, particularly the prefrontal cortex,” Gill explains. “On the other hand, heat stress also changes the balance of dopamine, serotonin, and acetylcholine, which are important for attention, learning, and memory.
“Sweating also depletes sodium, potassium, and other electrolytes, which affects nerve signaling and slows mental processing.”
How does dehydration during a heat wave affect our mood and mind?
“Even mild dehydration (1 to 2 percent loss of body weight in body fluids) can slow neural processing and impair memory, attention, and reaction time,” says Gill. “Dehydration increases cortisol and alters serotonin activity, leading to irritability, anxiety, and decreased frustration tolerance.
“Reduced blood volume and electrolyte imbalances limit the supply of oxygen and nutrients to the brain, causing a decline in mental performance.”
Here are some coping strategies that can help offset some of these effects.
Prioritize hydration with electrolytes
“Drink water regularly and include a source of electrolytes, not just when you’re thirsty,” Gill advises. “This helps maintain optimal brain signaling, prevent cognitive decline, and reduce irritation associated with dehydration.”
Maintain a cool sleep environment
“Try to maintain a consistent sleep-wake schedule. Use fans, blackout curtains, breathable bedding, and if possible, pre-cool your bedroom before bed,” recommends Gill. “Maintaining deep and REM sleep protects emotional regulation, memory consolidation, and decision-making ability.”
Practice stress adjustment adapted to the heat
“Do grounding and breathing exercises during the cooler parts of the day, as well as some light stretching and yoga in a shaded or air-conditioned area,” says Gill. “These regulate cortisol and keep the nervous system from going into a long-term ‘fight or flight’ state. ”
Plan your day without succumbing to the heat
“Schedule mentally demanding tasks during the cooler hours of the morning, and take regular breaks during peak heat,” suggests Gill. “This protects concentration and working memory, reducing errors caused by heat-related cognitive fatigue.”
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