How Stress Affects Your Body

Why do people experience stress? What does it do to the body? Ronesh Sinha, M.D., an internal medicine specialist at Palo Alto Medical Foundation, provides some answers. Q: What happens physically during times of stress?
Dr. Sinha: The stress response system was originally designed to keep people safe from environmental threats like hungry predators. Your body’s modern-day stress response is identical to that of your ancestors, preparing the body for a battle or a quick getaway, the classic “fight or flight” response. The body experiences a cascade of physical reactions, including:
  • An accelerated heartbeat.
  • Opening of lung airways to improve oxygen delivery.
  • Release of adrenaline to speed you up.
  • Release of glucose to power muscles.
  • Widened pupils to improve vision.
  • Lowered gastrointestinal activity so you can run, not digest.
For your ancestors, stress response activation was key to survival:
  • Tight blood vessels prevented excessive bleeding.
  • Elevated blood sugar gave energy to flee or fight.
  • Stored belly fat provided extra calories needed during times of scarcity.
  • Increased pulse and breathing maintained alertness during a crisis.
  • Tensed muscles served as a shield to protect vital organs.
Today, you rarely face a situation where you truly need to fight or flee. But your body still initiates the stress response in situations where there are no options for fighting or escaping: a traffic jam, a disagreeable boss or coworker, a looming deadline. In the modern, sedentary person, the same physiological stress responses your ancestors needed lead instead to high blood pressure, diabetes, central body obesity, palpitations and anxiety, and muscle tension and pain.

Q: How does stress affect the heart?

Dr. Sinha: In the movies, people who are under intense stress often seem to dramatically keel over from a heart attack, but that’s extremely rare. The real danger is the accumulated impact of chronic stress, which contributes to each of the top five risk factors for developing heart disease: abnormal cholesterol levels, diabetes, high blood pressure, obesity and smoking.

Q: How does stress affect the brain?

Dr. Sinha: Chronic stress can make your brain behave in an Alzheimer’s-like manner. Stress adversely affects a key structure in the brain, the hippocampus, leading to impaired memory and problems with orientation and sense of direction. These brain changes may have evolved to protect against the memory of traumatic and stressful events, like being attacked by a predator; but losing short-term memory hinders today’s brain-intensive lifestyle. We all recognize the frustration of forgetting where we put our keys, names of people we just met or other recent events. Nor does stress help you function any better on brain-intensive tasks. In one study, scientists studied brain blood flow while subjects performed tasks that required sorting large amounts of data—essentially stressful multitasking. They found that the prefrontal cortex, the “executive” part of the brain used for planning, execution, reasoning and organization, was initially very active but then tired and shut down. That left the “reptilian” brain, the impulsive and emotional brain, in charge. Pay attention to how your emotions transform in the midst of multitasking, typically moving from initial clarity to confusion and frustration.

Q: How does stress disrupt sleep?

Dr. Sinha: When you’re continually stressed, your body constantly pulses out stress hormones, which make it harder to fall asleep and impair the deepest stages of sleep. That can lead to hyperarousal insomnia—a state where your mind and body are easily woken by sounds or by your own stressful thoughts. No longer can you sleep as soundly as a baby.

Q: What about energy levels?

Dr. Sinha: Chronic stress can also make you tired. Your adrenal glands act like battery packs; they provide energy-producing substances such as adrenaline on demand, a key part of the stress response. Unfortunately, many people overuse these limited battery reserves with endless work and personal demands, leaving them depleted. The result: fatigue.

Q: Does stress make you age faster?

Dr. Sinha: As if heart disease, brain fog, lack of sleep and fatigue aren’t enough, chronic stress can also cause you to age more quickly than normal. One study compared a group of women caring for disabled children with a group of women whose children had no disabilities. In particular, the researchers compared their telomeres, protective sections of DNA that are known to be a genetic marker for aging. Telomeres routinely wither and get shorter with time, but external factors, including stress, can accelerate this process. The study found more prominent premature aging in the high-stress mothers caring for disabled children. In fact, it translated into that group being 10 years older at a cellular level than the other group, who were the same chronological age. The 35-year-old stressed mothers looked closer to 45. Bottom line? Keep an eye on how stressed you are and what you can do about it. Your body will thank you.