How Does Stress Affect Your Work?
Quick answer:
Stress is your body’s response to a demand. A short burst can sharpen you up, but intense or lasting stress makes it harder to hold information in mind, change tack and ignore distractions, which is what complex work needs. Reading your own sense of strain alongside trends in your sleep and heart rate variability helps you spot it early and plan around it.The most stressful days at work are rarely the quiet ones. You answer forty emails, join three calls and fix a problem nobody else had noticed, and at six o’clock the business case you meant to finish is unchanged. It’s tempting to blame your discipline, but a better explanation is that stress has changed which kind of work your brain finds easy: quick, reactive tasks feel effortless, and slow, careful thinking gets much harder.
The most stressful days at work are rarely the quiet ones. You answer forty emails, join three calls and fix a problem nobody else had noticed, and at six o’clock the business case you meant to finish is unchanged. It’s tempting to blame your discipline, but a better explanation is that stress has changed which kind of work your brain finds easy: quick, reactive tasks feel effortless, and slow, careful thinking gets much harder.
It’s a common day. In the American Psychological Association’s 2023 survey of 2,515 US employees, 77% had felt work-related stress in the previous month and one in five said it had made them less productive (APA, 2023). In Great Britain, the Health and Safety Executive estimates that work-related stress, depression or anxiety affected 964,000 workers in 2024/25, with 22.1 million working days lost (HSE, 2025).
Knowing what’s happening in your body and brain won’t move the deadline, but it gives you more say over how you use the hours you have.
What stress does to your body
Any demand, whether it’s a deadline, friction with a colleague or worry about your job, is a stressor, and stress is how you respond to it. That’s why the same presentation can feel manageable one week and overwhelming the next, depending on what else is going on. Acute stress passes once the demand does, whereas chronic stress carries on or keeps coming back (NIMH).
When your brain decides something needs dealing with, it switches on two connected systems. The first is fast: your sympathetic nervous system triggers the release of adrenaline, your heart rate climbs and your body gets ready to act. The second, known as the hypothalamic-pituitary-adrenal (HPA) axis, works more slowly, passing hormonal signals from the brain to the pituitary gland and on to the adrenal glands, which release cortisol to make energy available (Chu et al., 2024). At your desk, the result might be tight shoulders or a racing heart before a difficult call.
Cortisol has a bad reputation, but it does essential everyday work, including regulating metabolism, and a rise during a challenge is a normal part of the response. The trouble starts when the response never gets the chance to switch off. Persistent stress can contribute to headaches, digestive problems and poor sleep, which is how you end up exhausted by evening yet lying awake. Your body needs regular gaps between demands for the response to settle (MedlinePlus).
How stress changes your thinking
Much of the heavy lifting in knowledge work happens in the prefrontal cortex, the part of the brain that handles planning and keeps information in mind while you use it. Under intense stress, a surge of the chemical messengers noradrenaline and dopamine weakens the networks it relies on, and control shifts towards quicker, habitual responses to whatever feels most urgent (Arnsten, 2009). That’s helpful when the threat is physical, and far less helpful when it’s a business case due on Friday.
The impact of stress on cognition is complex, and the ‘ideal’ level of stress can depend largely on the job in hand. A meta-analysis of 51 studies and nearly 2,500 participants found that, on average, acute stress impaired working memory, the mental workspace where you hold and juggle information, and cognitive flexibility, your ability to change tack when something new comes up. The effect on working memory was small overall but grew on tasks that asked people to hold more in mind, and stressed participants also found it harder to keep distracting thoughts out (Shields et al., 2016).
These were laboratory tests, so they can’t predict how any one person performs at work, but the pattern is easy to recognise. With the business case, it might look like losing track of the assumptions behind your financial model, sticking with the original plan despite receiving new figures, or drifting back to a difficult conversation every time you start a paragraph, rather than focusing on the task in hand.
The most useful response is to ask less of your working memory. Write the assumptions down, take the questions one at a time and give anything consequential a second check. This is where your task manager and calendar earn their keep, because every step that lives in a list is one less thing your stressed brain has to hold.
When pressure helps, and when it doesn’t
Pressure isn’t always bad for you. The nerves before a big presentation can sharpen your attention and push you to prepare properly, and this manageable, motivating kind of stress is sometimes called eustress, as opposed to distress. Which one you get depends on how you perceive the stressor, on how intense the stress is, how long it lasts, how much control you have and what you’re trying to do.
The most telling sign is what happens afterwards. If you can settle once the deadline has passed, the pressure probably did its job, but if the tension follows you into evenings and weekends, there’s very little room left for recovery.
How to tell how stressed you are
No single number captures stress, because how you feel and how your body responds tell you different things. Start with how you feel: how overwhelmed are you, what’s driving it and can you switch off? For something more structured, the validated Perceived Stress Scale asks how stressful life has felt over the past month (Cohen et al., 1983). It’s useful for tracking your experience over time but can’t diagnose anything, so if you’re worried about how you’re feeling, speak to a health professional.
Your wearable adds a physiological view through heart rate variability (HRV), the variation in time between heartbeats. Stress is often linked to lower HRV, although findings and measurement methods vary (Kim et al., 2018). Exercise, illness, alcohol and poor sleep affect it too, so a single low reading can’t tell you why it’s low. The value is in the trend: compare readings with your usual range, measured the same way each time, alongside your resting heart rate, how long you slept and how you feel. Our guide to HRV and work explains how to read your own pattern, and if checking the numbers starts to wind you up, our piece on wearable data anxiety is worth a read.
Cortisol is harder to pin down, because levels rise and fall naturally through the day (MedlinePlus), and the stress score on your device doesn’t measure it directly. That is starting to change. Sweat sensors have now tracked cortisol over time in very small studies, including a cold-stress experiment with five volunteers (Cho et al., 2026), and more practical options for constant cortisol monitoring are likely over the next few years.
What helps at work
Start with the cause. If the work won’t fit the time available, make the trade-off explicit: which deadline can move, what can be scaled back and where do you need help? Pressure that persists week after week needs a conversation about how work is organised across the team (NHS).
For the work that remains, make the next step smaller. ‘Finish the business case’ is a heavy thing to carry around, whereas ‘draft the recommendation and list the questions I can’t answer yet’ is something you can start this afternoon. Close the notifications you don’t need and protect time for that one step.
Give recovery a proper place in the day, whether that’s a break between demanding tasks, a walk or some slow, comfortable breathing. A meta-analysis of 12 randomised trials found breathing practices modestly reduced how stressed people felt, though most of the studies had a moderate risk of bias (Fincham et al., 2023). A regular sleep routine and time with supportive people help too (NHS). If you have little control over your calendar, ask your manager for support, and if stress persists or starts to affect your daily life, talk to your GP or a mental health professional.
How to use this with Phase
Phase reads your bio data, including your sleep, HRV and cycle data, translates it into a cognitive profile and maps that against your tasks and calendar to give you an alignment score: how well the work you’ve planned fits the state you’re in today.
Recognising stress is only useful if it changes what you do next, whether that means rearranging the week or taking something off the list. Join the waitlist and you’ll be eligible for 25% off when Phase launches.
The information in this post is for educational purposes only and does not constitute medical advice. If you have concerns about your health or wellbeing, please consult a qualified healthcare professional.
References
American Psychological Association (2023) 2023 Work in America Survey: Workplaces as engines of psychological health and well-being. Available at: apa.org.
Health and Safety Executive (2025) Work-related stress, depression or anxiety statistics in Great Britain, 2025. Available at: hse.gov.uk.
National Institute of Mental Health (n.d.) I'm So Stressed Out! Fact Sheet. Available at: nimh.nih.gov.
Chu, B., Marwaha, K., Sanvictores, T., Awosika, A.O. and Ayers, D. (2024) 'Physiology, stress reaction', StatPearls. Available at: ncbi.nlm.nih.gov.
MedlinePlus (n.d.) Stress and your health. Available at: medlineplus.gov.
Arnsten, A.F.T. (2009) 'Stress signalling pathways that impair prefrontal cortex structure and function', Nature Reviews Neuroscience, 10, pp. 410-422. doi: 10.1038/nrn2648.
Shields, G.S., Sazma, M.A. and Yonelinas, A.P. (2016) 'The effects of acute stress on core executive functions: a meta-analysis and comparison with cortisol', Neuroscience & Biobehavioral Reviews, 68, pp. 651-668. doi: 10.1016/j.neubiorev.2016.06.038.
Cohen, S., Kamarck, T. and Mermelstein, R. (1983) 'A global measure of perceived stress', Journal of Health and Social Behavior, 24(4), pp. 385-396. Scale resources available at: cmu.edu.
Kim, H.G., Cheon, E.J., Bai, D.S., Lee, Y.H. and Koo, B.H. (2018) 'Stress and heart rate variability: a meta-analysis and review of the literature', Psychiatry Investigation, 15(3), pp. 235-245. doi: 10.30773/pi.2017.08.17.
MedlinePlus (n.d.) Cortisol test. Available at: medlineplus.gov.
Cho, S., Shajari, S., Xiong, Y. et al. (2026) 'Wearable lateral flow assays for cortisol monitoring with time-dynamic sweat sampling and sensing by electrochromic timers', Nature Sensors, 1, pp. 85-98. doi: 10.1038/s44460-025-00005-z.
NHS Every Mind Matters (n.d.) Work-related stress. Available at: nhs.uk.
Fincham, G.W., Strauss, C., Montero-Marin, J. and Cavanagh, K. (2023) 'Effect of breathwork on stress and mental health: a meta-analysis of randomised-controlled trials', Scientific Reports, 13, 432. doi: 10.1038/s41598-022-27247-y.
NHS (n.d.) 10 stress busters. Available at: nhs.uk.
Medical Disclaimer
The information in this post is for educational purposes only and does not constitute medical advice. If you have concerns about your health or wellbeing, please consult a qualified healthcare professional.
Photo credit - Tim Van De Kuip on Unsplash
