Understanding the have-knots: The role of stress in just about everything

December 2007 Observer. Click here for more information.

Stress, to put it bluntly, is bad for you. It can kill you, in fact. A study now reveals that stress causes deterioration in everything from your gums to your heart and can make you more susceptible to everything from the common cold to cancer. Thanks to new research crossing the disciplines of psychology, medicine, neuroscience, and genetics, the mechanisms underlying the connection are rapidly becoming understood.

The first clues to the link between stress and health were provided in the 1930s by Hans Selye, the first scientist to apply the word “stress”— then simply an engineering term— to the strains experienced by living organisms in their struggles to adapt and cope with changing environments.

One of Selye’s major discoveries was that the stress hormone cortisol had a long-term effect on the health of rats.

Cortisol has been considered one of the main culprits in the stress-illness connection, although it plays a necessary role in helping us cope with threats. When an animal perceives danger, a system kicks into gear: A chain reaction of signals releases various hormones — most notably epinephrine (“adrenaline”), norepinephrine, and cortisol — from the adrenal glands above each kidney.

These hormones boost heart rate, increase respiration, and increase the availability of glucose (cellular fuel) in the blood, thereby enabling the famous “fight or flight” reaction.

Because these responses take a lot of energy, cortisol simultaneously tells other costly physical processes — including digestion, reproduction, physical growth, and some aspects of the immune system — to shut or slow down.

When occasions to fight or flee are infrequent and threats pass quickly, the body’s stress thermostat adjusts accordingly: Cortisol levels return to baseline (it takes 40-60 minutes), the intestines resume digesting food, the sex organs kick back into gear, and the immune system resumes fighting infections.

But problems occur when stresses don’t let up —or when, for various reasons, the brain continually perceives stress even if it isn’t really there.

Stress begins with the perception of danger by the brain, and it appears that continued stress can actually bias the brain to perceive more danger by altering brain structures such as those which govern the perception of and response to threat. Prolonged exposure to cortisol inhibits the growth of new neurons, and can cause increased growth of the amygdala, the portion of the brain that controls fear and other emotional responses.