What does stress really do to our bodies, and when does it become a big problem? From an elevated heart rate to weakened immunity, experts explain the hidden physical costs of chronic stress, and why our bodies aren't built to stay on high alert.
The Immediate Physical Response to Stress
When you wake up late, check your phone to find a social media firestorm, deal with missing shoes and a bus lane fine, your body responds by ramping up biological systems that evolved for ancient threats. "The most immediate effect we see in a stressful situation is a surge of adrenaline causing an increase in heart rate, blood pressure and breathing," says Prof Kavita Vedhara, a specialist in stress and behavioural medicine at Cardiff University. "This is your fight-or-flight response, and it's designed to prepare you to address the challenge you are facing."
Within about 30 minutes, cortisol levels rise. "Again, this is very useful in supporting the fight-flight response because it regulates blood pressure, suppresses inflammation and increases the availability of blood sugars to increase energy," says Vedhara.
When Stress Becomes Chronic
Centuries ago, stress responses were useful for physical challenges. But today, we rarely need to fight or flee from stressors, yet we ruminate on arguments or online criticism. When the body diverts resources to fight or flight, it neglects digestion, repair and immune function. "Perhaps the most well-known issue associated with chronic stress is poorer immune function, which can increase risk of infections, make vaccines work less well, impair wound healing, and so on," says Vedhara. "But chronic stress has also been shown to increase the risk of obesity, depressive illness and progression of neurodegenerative diseases such as Alzheimer's."
The Feedback Loop of Anxiety
Dr Jo Daniels, a senior lecturer in psychology at the University of Bath, explains: "Because of the complex physiological nature of the stress response, we often experience a range of changes in the body. This in itself can become alarming for some people: why is my heart beating so fast? This can then trigger increased attention to what are essentially normal bodily variations, which effectively amplifies those physiological sensations, adding another layer of stress and anxiety."
"When we're in a stress response, we're hypervigilant, so we're more likely to consider normal variations in our bodily sensations to be threatening," Daniels adds. "Because we are flooded with stress hormones and using that ancient part of our brains programmed for survival, our decision-making is also likely to be impaired."
How Much Stress Is Too Much?
Scientists are still determining thresholds. "It's an elastic system – it's designed to respond and recover," says Vedhara. "It's certainly true that the experience of stress has such wide-ranging effects on our physiology that there is potential for it to take a very real toll on our health and wellbeing – but that's only true for long-term and enduring stressors."
In a landmark 1990s study, researchers found that stressed volunteers were more likely to become ill after exposure to the common cold. Older adults may see worse effects, but tolerance varies. "A lot depends on your life experiences," says Daniels. "People who have been affected by trauma might have a lower threshold for stress response – while other people seem to seek out stressful careers and thrive in them."
Managing Stress: Simple Strategies
One evidence-backed option is slow breathing. "When people are stressed or anxious, they tend to breathe in a more shallow and rapid way, which reinforces the threat response," says Daniels. "If you breathe slowly, you're giving your brain the message that everything is OK, you are safe – essentially inducing the relaxation response." Exercise can also help reduce excess adrenaline buildup.
For prolonged stress, cognitive behavioural therapy (CBT) can help challenge unhelpful thoughts like "I can't cope." "A helpful strategy can be to sit down and assess the evidence – have you coped before? And with worse?" says Daniels. Mindfulness-based stress reduction teaches stepping back from thoughts rather than challenging them.
When to Seek Help
Avoiding stress completely isn't realistic. "Catch your stress response early, and you have a good chance of reversing it using simpler strategies – but for chronic stress, modifications to lifestyle, accessing social support and developing helpful coping skills are key," says Daniels. "I would suggest people seek help when they are experiencing stress most or all of the time, or if they themselves are concerned about their stress levels."
