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Stress

Negative effects of excess

Stress hormones, in preparing the body for the fight or the flight, cause blood to be shunted away from nonessential areas, including the liver, which filters away cholesterol. It has been associated with:

back pain
depressed immune response
hair loss
even situational homosexuality
irritable bowel syndrome

In medical students studying for exams, the medial prefrontal cortex shrinks during cram sessions but grows back after a month off.

Moderation

While moderate stress is desirable for performance, chronic stress is not.

Relax periodically

The findings, published in the American Journal of Epidemiology in 1992, reported that the least frequent vacationers (those who took no more than one vacation every six years) were at 50% higher risk for a heart attack than the most frequent vacationers (those who took at least two vacations every year). [Ref]
People who took an afternoon nap of 30 minutes or more at least three times a week had a 37% lower risk of dying from heart disease than those who did not. [Ref]