As Britain gears up for its first heatwave of the year, with temperatures expected to hit the mid-30s Celsius, the typical excitement for sunny weather may be tempered by growing unease. Beyond the immediate physical discomfort and fatigue, prolonged high temperatures are increasingly affecting our mental health and emotional state. To delve into the psychological effects of heatwaves and explore ways to stay balanced, The Independent consulted Dr Ravi Gill, a practitioner psychologist.
Can heatwaves affect our mood?
Physiological changes in the body and brain due to heat can significantly influence mood during a heatwave. “Heat disrupts neurotransmitter systems like serotonin, impairs sleep, and raises stress hormones such as cortisol, which are key regulators of mood and impulse control,” says Dr Gill. The physical discomfort and disrupted sleep from heatwaves can also worsen mood instability, trigger anxiety spikes, or increase irritability. “Lingering discomfort and environmental stress strain emotional resilience, making even minor irritants feel overwhelming,” adds Gill. “Heatwaves can also escalate social tensions – whether at home, in traffic, or public spaces – turning minor triggers into conflicts.” Research indicates that individuals with pre-existing mental health conditions are more vulnerable during heatwaves. “Conditions such as anxiety, depression, bipolar disorder, or schizophrenia can make it harder to recognise early signs of heat stress or to take action,” notes Gill. “Additionally, some psychiatric medications, including antipsychotics, certain antidepressants, and mood stabilisers, reduce the body’s ability to sweat or regulate temperature, increasing the risk of heat exhaustion or heatstroke.”
How do heat-related sleep disturbances impact mood?
“High nighttime temperatures make it harder for the body to drop its core temperature, which is essential for initiating and maintaining deep, restorative sleep,” says Gill. “People wake more often, particularly during REM sleep, which is vital for emotional processing and memory consolidation. Difficulty falling asleep and staying asleep reduces overall rest.” This can profoundly affect emotional regulation. “Poor sleep lowers activity in the prefrontal cortex, responsible for impulse control, and heightens amygdala reactivity, linked to fear, anger, and anxiety. This makes us more emotionally volatile,” explains Gill. “Lack of REM sleep amplifies stress responses and reduces resilience to everyday frustrations. Sleep deprivation also impairs attention, working memory, decision-making, and problem-solving, increasing mental fatigue.”
What impact do heatwaves have on cognitive functions?
“Heatwaves can impair core cognitive functions like memory, focus, and decision-making, due to a mix of direct brain effects and secondary factors like dehydration and sleep disruption,” says Gill. Factors such as reduced cerebral blood flow, neurotransmitter disruption, and electrolyte imbalance can significantly affect cognitive function. “High temperatures cause blood vessels to dilate and divert blood towards the skin for cooling, reducing blood flow and oxygen delivery to the brain’s thinking centres, especially the prefrontal cortex,” explains Gill. “Heat stress also alters the balance of dopamine, serotonin, and acetylcholine, which are critical for attention, learning, and memory. Sweating depletes sodium, potassium, and other electrolytes, affecting nerve signal transmission and slowing mental processing.”
How does dehydration affect mood and mind during heatwaves?
“Even mild dehydration, defined as 1-2 percent body weight loss in 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 lower frustration tolerance. Reduced blood volume and electrolyte imbalances limit oxygen and nutrient delivery to the brain, causing mental sluggishness.”
Four coping strategies to counterbalance heat effects
Prioritise hydration with electrolytes – “Drink water regularly, not just when you feel thirsty, and include electrolyte sources,” advises Gill. “This helps maintain optimal brain signalling, prevents cognitive slowing, and reduces irritability linked to dehydration.”
Maintain a cooling sleep environment – “Try to keep a consistent sleep-wake schedule. Use fans, blackout curtains, breathable bedding, and, if possible, pre-cool your bedroom before sleep,” recommends Gill. “Preserving deep and REM sleep protects emotional regulation, memory consolidation, and decision-making capacity.”
Practise heat-adapted stress regulation – “Use grounding or breathing exercises in cooler parts of the day – gentle stretching or yoga in shaded or air-conditioned spaces can also help,” says Gill. “These regulate cortisol and keep the nervous system from staying in a prolonged fight-or-flight state.”
Structure your day around the heat – “Schedule mentally demanding tasks for cooler morning hours and take regular breaks during peak heat,” suggests Gill. “This protects focus and working memory, reducing mistakes caused by heat-related cognitive fatigue.”
