What stress does to your health after a day, a week, a month, and a year
Stress is a natural process that can be beneficial in some instances, but highly detrimental in others. The biological ‘fight or flight’ response evolved millions of years ago to protect early humans from physical threats, and we have carried it through to the modern day where the threats are very different. We’re no longer being chased by predators or living in caves, but data suggests we’re more stressed than ever. The Mental Health Foundation reports that over three-quarters of adults (78 per cent) have felt so stressed at some point in the last year that they felt overwhelmed or unable to cope. According to Mental Health UK, nine in 10 (91 per cent) of UK adults experienced high pressure or stress at some point in 2024. “Stress levels across the UK have increased in recent years,” says Dr Reem Hasan, NHS GP and Chief Medical Officer at Vista Health. “I see this frequently across my patient group, and its impact on mental and physical health.” She cites several underlying reasons, including the ongoing cost-of-living crisis, workplace demands, and family or caring responsibilities. 'Healthy' stress
She emphasises that some stress is inevitable, and can even be helpful. “Healthy stress can help us perform better, stay alert, and achieve goals. It’s the body’s way of preparing for challenges with increasing focus, energy, and motivation. However, unhealthy or chronic stress occurs when those pressures become constant or feel uncontrollable.” The difference, she says, depends on the duration, how you respond (with control or panic), and whether or not you rest. We spoke to the experts to understand exactly what happens to our health when we experience short and long term stress, and the best, science backed ways to manage it.
After an hour
Stressors can pop up out of nowhere: suddenly receiving an urgent complaint at work; a delay on the tube making you late for an appointment. Whatever the trigger might be, the brain interprets it as a threat and swings into action, prompting the release of stress hormones that put the rest of the body on high alert, says Adriana Kober, a clinical psychologist at the Priory Group. The immediate effects can include a sense of fear and worry. “The prefrontal cortex is temporarily impaired, which affects decision making and focus,” she says. “There’s also difficulty in concentrating on multitasking: our brain is in survival mode.” However, under stress, our dopamine levels also rise, leading to enhanced alertness and attention: “Our reflexes are quick and we’re very reactive, both physically and emotionally.
Acute stress
How you react to acute stress depends on what in psychology is called the cognitive appraisal process. If you perceive the demands on you to be beyond your ability to manage, the stressor is interpreted as a threat; but if you perceive them as challenging but manageable, the stressor is simply a challenge. This response is subjective and shaped by both nature and nurture. Acute stress leads to raised blood pressure and heart rate, as “the body diverts resources to functions essential for immediate survival like your brain and muscles”, says Dr Hasan. “Your breathing rate increases to speed up distribution of oxygen-rich blood, your muscles tense, and functions like insulin sensitivity and digestion take a back seat.” Another positive effect is on immunity – short term stress stimulates the immune system, and which can aid the control of inflammation, she says.
After a day
It’s not unusual for stress to lead to digestive symptoms – either slowing it down or speeding it up, says Dr Hasan. “It’s not clear cut why it goes one way or the other but blood being diverted away from the digestive system can result in symptoms like bloating, indigestion, constipation, or if it speeds it up you’ll get symptoms like diarrhoea or cramping. It’s also going to increase acid production in your stomach so you’re more likely to get acid reflux or gastritis. If you suffer with anything under the umbrella of Irritable Bowel Syndrome, stress will definitely trigger or worsen it.” Meanwhile muscle tension from a stressful day can result in headaches and aches and pains, particularly in the back, neck, shoulders and jaw. How to combat it: If you think acute stress is causing or worsening health symptoms, incorporate time into your day to relax. Experts recommend exercise – even dancing or shaking your body – taking a walk outside in nature, or breathing exercises. A systematic review found belly breathing – engaging the diaphragm and deep breathing – can reduce stress and cortisol levels.
After a week
Stress is most beneficial for acute periods of time, and once dealt with, the responses should dissipate. But if the nervous system stays on high alert as the social stressor continues, it can have negative impacts. “If we have a week of ongoing stress, it keeps us emotionally on edge all the time,” says Kober. “The prefrontal cortex function continues to decline, meaning reducing cognitive flexibility. There’s poor impulse control” – this could look like snacking, boozing, or spending impulsively – “and the hippocampus, which is the memory centre, starts to show signs of stress-related dysfunction.” This means planning will become much harder, as will keeping track of plans and staying on focus. A week of sustained stress is also likely to impact sleep. Fight or flight causes mental and physical hyperarousal, making it much harder to relax. “After a few days of sleep disruption, our REM and deep sleep is affected, which the body needs to really rest,” Kober says. “Then this all affects memory consolidation and the way that we regulate our mood.”
Effects on the digestive system
Physiologically, Dr Hasan says that sustained high blood pressure and heart rate, even over a relatively short duration, can still elevate your cardiovascular risk. Additionally, “that persistent muscle tension is going to lead to soreness, often jaw pain, reduced mobility. At this point, stress can begin to lower your immune efficiency. You’re beginning to be a little bit more susceptible to minor infections as your baseline has been lowered”. Stress also disrupts the balance and communication between the gut and the brain which can lead to GI symptoms, Dr Hasan says. “So even in the absence of physical disease, the disruption of the gut brain axis can create IBS problems.”
How to combat it
At this early stage of a stressful period, establishing good habits can prevent or reduce impacts on health. Sleep should be a priority. Establish a clear routine – getting up at the same time every day, to regulate circadian rhythms and the release of stress and sleep hormones. Finding ways to manage everyday stress can help keep chronic diseases under control. A study last year by Kings College London found interventions to improve mood, such as exercise, antidepressants and therapy, reduced inflammation in people with inflammatory bowel diseases such as Crohn’s disease.
After a month
“If stress goes on for a month, that’s constant activation of the stress response,” Dr Hasan says. “Your blood pressure may now be chronically elevated, which is setting the stage for hypertension.” This level of prolonged inflammation is likely to provoke flare ups if you’ve got an already underlying inflammatory condition like arthritis or colitis, she says, while “your chronic muscle tension is now going to lead to back pain and reduced exercise tolerance. When it’s impacting something that can positively impact your stress, then it’s a vicious cycle.” Elsewhere in the body, elevated levels of stress hormones over weeks and months can disrupt the production of other hormones in the body, leading to potential interference with sperm production and erectile dysfunction or impotence in men, or delays of the menstrual cycle or other fertility processes. And the impact on your sleep will be compounding into fatigue which will exacerbate other psychological effects.
How to combat it
“The brain starts changing already and hippocampal atrophy begins which affects our memory,” says Kober. She adds that the prefrontal cortex can shrink under prolonged stress – meaning we are less flexible, more impulsive, and more prone to rumination and negative self-focus. “When we’re ruminating and losing focus, we’re forgetting about our basic needs and what actually used to work for us.” Sleep, relaxation and nutrition can all fall by the wayside, meaning we can reach for the more comforting, less nutritious options. This is exacerbated by the gut response to stress, Dr Hasan says. “When stress is prolonged, even just by a week, it will begin to alter your gut microbiome which is going to impact both immunity and nutrient absorption, and also increase your cravings for the wrong foods – high fat, sugary foods.” How to combat it: While some stress is unavoidable, it’s important to identify the cause of it and seek ways to alleviate it. Experts recommend setting boundaries with colleagues or friends, and being realistic about your limits.
After a year or more
“Chronic stress increases what I would consider serious health problems,” Dr Hasan says. “Your risk of cardiovascular disease, heart disease, stroke, type two diabetes will increase, and that risk for stroke or heart attack is conflated if you’ve got type two diabetes.” One US study of more than 5,000 adults found that stress ages the immune system – researchers said unhealthy habits associated with stress such as smoking, drinking, and a bad diet played a part in this. Prolonged strain on the musculoskeletal system becomes much harder to recover from, leading to constant aches and pains and less motivation or ability to exercise/stretch to fix them. In the digestive system “when things become chronic, it can also manifest as gastric ulcers: stomach ulcers or persistent bowel inflammation. That puts you at increased risk of other bowel conditions as well”
Effects on cognitive function
A 2023 study of 24,000 people aged 45 and over found that people with chronic, elevated stress were 37 per cent more likely to have poor cognitive function. “Chronic stress for a year or more accelerates brain aging and increases risk of Alzheimer’s or dementia,” says Kober. “It reduces the grey matter in the brain, there’s shortening in brain cells, meaning that the cells are aging much faster, and it affects our cognitive impairment. We know that years of prolonged exposure to stress hormones is associated with accelerated aging, reduced resilience, and a greater likelihood of chronic diseases across the spectrum,” Dr Hasan adds. “Structural, functional brain changes might contribute to mood disorders like depression and anxiety. The persistent inflammation raises our risk of cancers, neurodegenerative diseases like dementia and frailty.”
How to combat it
Once stress becomes chronic it can be harder, but not impossible, to recover from the impacts on the body and mind. One of the best things you can do to lower inflammation from stress is to exercise. It can reduce your levels of stress hormones, and by getting your heart rate up you will also counter the impact of stress on your cardiovascular system. A healthy diet and good sleep pattern are also vital, along with psychoeducation – learning about mental health and wellbeing. Increasing research shows that loneliness is one of the most dangerous forms of chronic stress, and ages the brain and body. Seek positive ways to connect with people in real life. Take a look at your working hours, too: in 2021, a study in the journal Environment International showed people working more than 54 hours a week are at significant risk of dying from strokes and heart attacks.
