The Biology of Stress
Imagine you are a zebra grazing on the plains of Africa. It's midday. The sun is bright, the food is plentiful.
Suddenly you sense an attack. A lion is chasing you. Its fight or flight in action.
Your brain tells your body to prepare for a fight or take flight. The body responds by preparing extra hormones to create more energy and by increasing the rate the heart pumps blood to the muscles. For most animals, this stress reaction lasts for just a short time and it saves lives.
Why don’t zebras get ulcers? According to Dr. Robert Sapolsky, their stress is decidedly short term, not long term.
As a body is preparing for fight or flight, however, practically all systems, such as digestion, physical growth, and warding off diseases are placed on hold. This means that people for whom stress has become a way of life are endangering their overall health. Researchers have learned by studying primates whose systems are similar to human beings that those who learn to have control over their lives and are able to reduce or avoid stress live longer and healthier lives.
Are zebras better equipped to deal with stress than humans? No. However, according to Dr. Robert Sapolsky, author of Why Zebras Don't Get Ulcers, "For a zebra, stress is three minutes of some screaming terror running from a lion. After the chase, either it's over or they are." On the other hand humans, he says, have constructed a network of social stressors. Since we are obliged to live in this framework, stress builds up.
While the stress response activates automatically, its duration and intensity relies on factors such as individual temperament.
How do the brain and the body react to stress? Stress, such as the threat of attack, forces various changes in the body. First, adrenaline causes an increase in heart rate and blood pressure so that blood can be sent to muscles faster. Second, the brain’s hypothalamus signals the pituitary gland to stimulate the adrenal gland (specifically the adrenal cortex) to produce cortisol.
This stress hormone, a longer-acting steroid, helps the body to mobilize energy. However, prolonged exposure to cortisol can damage virtually every part of the body. Chronic high blood pressure can cause blood vessel damage and the long-term shutdown of digestion can lead to ulcers.
Stress, such as the threat of attack, forces changes in the body carried out by the hypothalamus-pituitary-adrenal axis (HPA).
Why do some people experience more stress than others? Individuals who feel they have control over their lives appear to experience less stress. It also depends on personality and temperament. Aggressive, competitive types are more likely to define a situation as stressful than a passive, accommodating personality. A universal stress producer seems to be social isolation.
PTSD: A Breakthrough in Diagnosis
In 1980 the mental health community established the diagnosis of Post Traumatic Stress Disorder, PTSD, and revolutionized the way the field views the effects of stress. This change acknowledged that many of the symptoms people experience after exposure to trauma can be long-lasting, if not permanent. Before that shift, the field tended to view stress-related symptoms as a transient, normal response to an adverse life event, not requiring intensive treatment.
Furthermore, before 1980, people who did develop long-term symptoms following trauma were viewed as implicitly vulnerable; the role of the actual event in precipitating their symptoms was minimized. For a while, in a reversal of previous thinking, experts expected most trauma survivors to develop PTSD. More recent research has confirmed that only about 25 per cent of individuals who are exposed to trauma develop PTSD.
So who is likely to develop PTSD following a traumatic experience, and why? The answer is not yet clear, but it now appears that PTSD represents a failure of the body to extinguish or contain the normal nervous system response to stress. This failure is associated with many factors:
- the nature and severity of the traumatic event
- preexisting risk factors related to previous exposure to stress or trauma, particularly in childhood
- the individual’s history of psychological and behavioral problems, if any
- the person’s level of education, and other cognitive factors
- family history—whether parents or other relatives had anxiety, depression, or PTSD
People who develop PTSD are also more likely to develop other psychiatric disorders involving mood (depression, anxiety and panic, bipolar disorder), personality, eating, and substance dependence.