Understanding Stress: Hans Selye’s Three Stages and the Toll on Your Body
In 1936, pioneering scientist Hans Selye discovered something fascinating: no matter what kind of toxin he introduced into lab animals, their bodies reacted in the same way. He noticed three consistent changes:
- The adrenal glands swelled
- The lymph nodes and immune structures shrank
- Bleeding ulcers formed in the stomach and intestines
These observations led Selye to develop a theory that would change the way we understand stress. He called it the General Adaptation Syndrome (GAS) — the body’s predictable pattern of response to prolonged stress. This theory explains why chronic stress doesn’t just affect your mood, but your physical health too.
Let’s break it down:
Stage One: The Alarm Reaction
This is the body’s immediate response to a stressor — the classic “fight-or-flight” reaction. Your heart rate spikes, your muscles tense, your senses sharpen, and your body prepares to either face a threat or run from it.
But there’s a cost.
Your immune system temporarily shuts down, making you more vulnerable. If the stress is short-lived, your body returns to normal quickly. But if the stress continues…
Stage Two: Resistance
Now your body adapts. It works overtime to keep you functioning — strengthening the immune response and adjusting to the ongoing stress.
During this stage, you may feel like you’ve got it under control. In fact, your body may seem stronger than ever. But this isn’t sustainable. The longer you remain in this state, the more energy it takes to maintain — and eventually, something’s got to give.
Stage Three: Exhaustion
This is burnout. Your body can no longer keep up with the relentless demands. The immune system crashes. Organs start to malfunction. Chronic diseases start to appear — from ulcers and diabetes to heart disease and depression.
This final stage is what Selye called the “diseases of adaptation.”
How Do You Know If You’re Stressed?
Here are just a few common triggers:
- Working more than 40 hours a week
- Moving to a new home
- Taking out a loan or mortgage
- Experiencing loss (divorce, death, separation)
- Conflict at work or home
- Welcoming a new family member
- Financial instability
- High achievement or major life changes
Even if you’re not personally going through one of these, being close to someone who is — or simply living in a high-stress environment — can still affect your body.
What Does Chronic Stress Actually Do to Your Body?
Here’s a look at how stress impacts various systems:
- Adrenal Glands:
Pump out cortisol and other stress hormones. In excess, these suppress immunity and increase disease risk. - Thyroid Gland:
Speeds up metabolism. Result? Insomnia, anxiety, and exhaustion. - Hypothalamus:
Releases CRH (which triggers anxiety) and endorphins (your body’s painkillers). Under constant stress, endorphin levels crash — causing pain, fatigue, and mood swings. - Sex Hormones:
Progesterone and testosterone levels drop. This can lead to sexual dysfunction, menstrual irregularities, and hormonal imbalances. - Digestion:
Slows or shuts down. Eating under stress may cause bloating, nausea, cramping, or diarrhea. - Blood Sugar:
Spikes for a burst of energy, followed by insulin release. Chronic stress can lead to insulin resistance, hypoglycemia, or worsen diabetes. - Cholesterol:
Surges into your bloodstream — useful in emergencies, but dangerous when unused. It contributes to heart disease. - Heart & Lungs:
Heart rate and breathing increase. Over time, this can cause high blood pressure, stroke, and cardiovascular strain. - Blood:
Thickens and clots more easily under stress — a risk factor for stroke and heart attacks. - Skin & Senses:
Sweating, crawling sensations, and heightened sensory awareness are common. But prolonged hyper-alertness can lead to “sensory burnout,” reducing efficiency in your sight, hearing, and other senses.
Final Thoughts
Stress isn’t just “in your head” — it’s deeply physical. The longer it goes unchecked, the more it chips away at your body’s resilience. The good news? Understanding the stages of stress can empower you to take proactive steps toward better health.
Start small. Breathe. Take breaks. Prioritize rest. Move your body. Talk it out.
Your body is talking — are you listening?
