Stress is the body’s built-in response to perceived challenge, threat, or demand—whether physical (like injury or illness) or psychological (like work pressure or conflict). When you detect a stressor, your brain activates the sympathetic nervous system (“fight or flight”) and the HPA axis (hypothalamic–pituitary–adrenal axis), releasing stress hormones like adrenaline and cortisol. In the short term, this response is adaptive: it sharpens focus, mobilizes energy, and prepares you to act. The problem for physical health arises when stress is high, frequent, or unrelenting, and the stress response never really powers down.

Cardiovascular

One of the most direct physical effects of stress is on the cardiovascular system. During acute stress, heart rate and blood pressure go up, and blood vessels constrict in certain areas while dilating in others to prioritize blood flow to muscles and vital organs. This is useful in emergencies but problematic when it happens over and over, day after day. Chronic stress can keep blood pressure elevated and contribute to wear and tear on blood vessel walls, promoting arterial stiffness and atherosclerosis. Over time, this increases the risk of hypertension, heart attack, and stroke, especially when combined with other risk factors like smoking, poor diet, or lack of activity.

Metabolism

Stress also strongly influences metabolism and body weight through cortisol and other hormones. When you’re stressed, your body prepares for action by releasing stored energy—raising blood sugar and circulating fatty acids. If the stress is short-lived and followed by physical activity, this energy gets used. But with chronic psychological stress and little movement, blood sugar and insulin levels can stay higher than ideal, increasing the risk of insulin resistance and type 2 diabetes. Stress can also alter appetite: for some people it suppresses hunger, but for many it drives cravings for calorie-dense, sugary, or fatty foods (“stress eating”), which can contribute to weight gain, especially around the abdomen.

Immune System

TThe immune system is tightly linked to stress. Short-term stress can temporarily boost certain aspects of immune function, preparing the body to deal with potential injury or infection. However, long-term stress tends to suppress specific immune responses while promoting chronic low-grade inflammation. This imbalance can mean you’re more likely to catch infections, take longer to recover, and experience flare-ups of inflammatory conditions (like asthma, eczema, or certain autoimmune diseases). Over time, the combination of immune suppression and persistent inflammation is one way stress contributes to chronic disease risk.

Muscles & Posture

Stress affects muscles, posture, and pain. Many people unconsciously tense muscles in the neck, shoulders, back, or jaw when stressed. If this becomes habitual, it can lead to chronic muscle tightness, tension headaches, jaw pain, and back or shoulder issues. Stress also changes pain perception: when your nervous system is “on alert,” pain signals can feel louder and more intrusive. In chronic pain conditions, ongoing stress often creates a vicious cycle—pain increases stress, and stress amplifies pain—making both harder to manage. Relaxation, stretching, and movement help break this cycle partly by calming the stress response.

Digestive System

The digestive system is particularly sensitive to stress. Stress shifts blood flow away from the gut toward muscles and vital organs and changes how the gut moves and secretes enzymes and mucus. Acute stress might cause “butterflies,” nausea, or an urgent need to use the bathroom. Chronic stress can contribute to symptoms like indigestion, heartburn, constipation, diarrhea, or alternating bowel habits, and it’s closely linked to conditions like irritable bowel syndrome (IBS). Stress also interacts with the gut microbiome and immune cells in the gut lining, which can influence inflammation and overall digestive health.

Sleep

Stress has a major impact on sleep, which in turn affects physical health. High stress can make it harder to fall asleep, stay asleep, or reach deep, restorative sleep stages. Racing thoughts, elevated heart rate, and nighttime cortisol surges can fragment sleep or cause early awakening. Poor sleep then worsens stress tolerance, raises blood pressure, disrupts appetite hormones, and impairs immune function, creating a self-reinforcing loop. Over time, this combination of stress and sleep disruption can accelerate many stress-related health problems, from weight gain to cardiovascular issues.

Nervous System

The nervous system and brain change in response to prolonged stress in ways that show up physically. Chronic activation of the stress response can make the sympathetic nervous system dominate over the parasympathetic (“rest and digest”) system. This leaves your body in a sustained state of readiness—higher heart rate, tense muscles, shallow breathing—which is exhausting over time. The brain regions involved in threat detection and emotional regulation also adapt: you may become more reactive to minor triggers, which further ramps up physical stress responses like sweating, palpitations, and stomach discomfort, even in situations that aren’t truly dangerous.

Hormonal Balance

Stress influences hormonal balance beyond cortisol. It can disrupt the balance of sex hormones (estrogen, progesterone, testosterone), thyroid hormones, and growth hormone. In women, chronic stress may contribute to menstrual irregularities or more intense symptoms around the cycle. In men, long-term stress can be associated with lower testosterone levels, which can affect energy, muscle mass, and libido. Stress can also influence bone health indirectly by affecting hormones and behaviors (like nutrition and exercise) that regulate bone density. All of these hormonal shifts have downstream effects on physical health and how you feel day to day.

Behavior

Behavior is one of the main pathways through which stress impacts physical health. Under stress, people may sleep less, move less, and rely more on quick comfort behaviors—overeating, smoking, alcohol, or excessive screen time. These coping strategies can temporarily numb stress but generally worsen physical health markers like blood pressure, blood sugar, weight, and liver function. Over the long run, it’s often this combination—physiological stress plus less healthy habits—that drives much of the physical damage associated with chronic stress.

Effective stress management—through habits like physical activity, good sleep, supportive relationships, relaxation practices, and healthy boundaries—can significantly protect physical health. When you regularly activate the body’s “rest and digest” systems, blood pressure and heart rate trend lower, inflammation decreases, digestion improves, and sleep becomes more restorative. You’re better able to maintain healthy behaviors, like eating well and being active, because you’re not constantly running on empty. A well-managed stress response doesn’t mean you never feel stressed; it means your body can rise to challenges when needed and then reliably return to a calm baseline. Over time, this flexibility supports stronger immunity, healthier metabolism and cardiovascular function, less pain and tension, and greater resilience in the face of life’s inevitable ups and downs.

More Detail

Managing Stress