As a patient, dealing with the anxiety of waiting to get poked with a needle may be no fun at all. But it’s actually a positive behavior. In trials with mice, stress boosted the immune system, a team of Stanford University researchers found, making it vaccines more effective. Ferris Jabr reports for Scientific American:
Mice that were stressed out prior to their inoculations had an easier time overcoming a subsequent infection than mice that the researchers left in peace before their shots.
Something similar seems to happen to people. In a study of knee surgery patients, for example, Dhabhar and his teammates found that anticipating surgery increases the number of immune cells circulating in the bloodstream in the days preceding the operation.
While stress is generally thought of in terms of its negative effects, researchers are beginning to distinguish between two different types of stress. Chronic stress, suffered over a long period of time, can cause harm, whereas acute stress, like visiting the doctor or racing to meet a deadline, may actually make us stronger and healthier.
From an evolutionary perspective, the fact that short-term stress revs up the immune system makes sense. Consider a gazelle fleeing a lioness. Once the gazelle’s eyes and ears alert its brain to the threat, certain brain regions immediately activate the famous fight-or-flight response, sending electrical signals along the nervous system to the muscles and many other organs, including the endocrine glands—the body’s hormone factories. Levels of cortisol, epinephrine, adrenaline and noradrenaline rapidly increase; the heart beats faster; and enzymes race to convert glucose and fatty acids into energy for cells. All these swift biological changes give the gazelle the best chance of escape.
The brain also responds to stress by priming the immune system to prepare for a potential injury. This may explain why people and mice more readily respond to vaccines when they’re stressed out. So cry all you’d like in the waiting room – you may be doing your body a favor in the long run.
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