Stress and the Immune System

“A merry heart does good, like medicine, but a broken spirit dries the bones.”  – Proverbs 17: 22

“Trust in the Lord with all your heart and lean not on your own understanding … and it will be health to your flesh and strength to your bones.”  – Proverbs 3: 5 – 8

“…a good report makes the bones healthy.”  – Proverbs 15: 30








1.  Stress has an instantaneous effect on the brain

  • All incoming stimuli are scanned for danger (or uncertainty)
  • If any threats are perceived, the sympathetic nervous system goes into high alert and floods the body with chemicals to prepare it to meet the challenge 1

2.  Cortisol is considered the “stress hormone” because it is secreted in the bloodstream in higher levels during the body’s “fight or flight” response to stress

  • It acts as a temporary source of energy, allowing your body to respond to a perceived threat or stressor 2

3.  Cortisol is beneficial for a half hour or even a few hours, but over the course of days, weeks, etc. chronically high cortisol levels wreak havoc on the brain 3

4.  The area of the brain most affected by high stress or threat is the hippocampus

  • The hippocampus is very sensitive to cortisol
  • Too much/prolonged cortisol leads to significant physical changes to the brain–damaging existing neurons and interfering with neural production, especially hippocampal neurons
  • Combat veterans suffering from post-traumatic stress syndrome typically have 8-24% higher levels of atrophy (cell death) in the hippocampus (Sapolsky, 1999) 4

5.  The hippocampus is also the center of the body’s immune system

  • One study showed that stressed individuals were three times more likely to suffer from the common cold
  • According to the American Academy of Family Physicians two-thirds of doctor’s visits are for “stress-related conditions” 5

6.  Higher and more prolonged levels of cortisol in the bloodstream (like those associated with chronic stress) have been shown to have negative effects, such as:

  • Impaired cognitive performance
  • Suppressed thyroid function
  • Blood sugar imbalances such as hyperglycemia
  • Higher blood pressure
  • Decrease in muscle tissue
  • Decreased bone density 6

7.  It is interesting that the Scripture particularly makes a point of referencing bone health. The Bible is accurate in its neuroscience and in medicine.


  1. Source: Jensen, Eric Brain-Based Learning, 2008, Study cited: Sapolsky, R. (1999, March). Stress and your brain. Discover, 116, Medina, John, Brain Rules, 2008
  3. Jensen, Eric Brain-Based Learning, 2008
    Study cited: Sapolsky, R. (1999, March). Stress and your brain.Discover, 116
    Medina, John, Brain Rules, 2008
  4. Sapolsky, R et al (1985) Prolonged corticoid exposure reduces hippocampal neuron number: implications for aging J. of Neurosci 5: 1221
  5. Cohen SW et al (1991) Psychological stress and susceptibility to the common cold. New England Journal of Medicine 325: 606