October 6, 2012

How Placebos Work And Why Some Of Us Get Sick A Lot

One of my favorite old comedy skits is a 1970s Steve Martin routine.  Steve comes onstage and confesses to the audience that a doctor has given him some pain pills earlier, and now he’s as high as a kite.  He then whispers the name of the drug to the audience, in confidence. “They’re called . . . Placebos.”

Of course, we find the joke funny because we know that placebos don’t really do anything, which means that Steve Martin’s character is an overly suggestible idiot.

In reality, studies have shown that placebos, such as sugar pills, can help to relieve the symptoms of a disease.

Placebos are known to increase the immune response.

In 2002, Nicholas Humphrey proposed that placebos trick us into thinking that environmental conditions are better for launching a strong immune response.

According to a recent study, Siberian hamsters respond differently to infection depending on whether the lights above their cages replicate winter or summer conditions. The hamster’s immune systems worked harder when the lights were summery (long days, short nights) than when they were wintery (short days, long nights).

As reported in New Scientist, University of Bristol biologist Peter Trimmer also supports Humphrey’s theory.  Trimmer created a model to test it and found that an animal that lives in a challenging environment, where food is scarce, will live longer and produce more offspring if it tolerates infections without launching an immune response.

On the other hand, an animal living in a more favorable environment is better off launching an immune response, getting rid of the infection right away, and then going back to normal behavior.

This explains why the hamsters’ immune systems worked harder during what they thought were cold, harsh Siberian winters than in what they believed were milder Siberian summers.

An immune response uses up a great deal of energy, so firing up your immune system when you have to go out and find food during a time of scarcity can be fatal.  (Think of how much energy you have for normal activities when you have a bad cold.)

The results of Trimmer’s simulation prove that there is an evolutionary advantage to switching the immune system on and off depending on the environmental conditions.

Although the development of agriculture around 10,000 years ago means that many of us have stable food supplies and don’t have to worry about scarcity, our immune systems still work according to the principle that there are times when we can’t afford to fight off infection – we need to allocate all our energy to finding and securing food and to defending ourselves from predators.

Perhaps this explains why some people seem to catch colds all the time while others never get sick. Maybe people who become ill frequently had ancestors who came from mild environments where food was plentiful, so their immune systems were set up to be turned on more frequently,   while people who don’t seem to catch colds or the flu when everyone else is home sick in bed had ancestors who came from harsher environments and couldn’t afford to waste energy with strong immune responses.

This theory can also explain why nowadays some people (including myself) don’t get sick when they have to deal with an important situation, such as going on job interview or giving a presentation, but as soon as it is over and they are no longer under stress, their immune systems catch up and they find themselves afflicted with the same cold that everyone else got over a week ago.

Although we no longer have to struggle to find food, many of us still engage in tasks that take up a great deal  of energy, and our immune systems may be set up to accommodate this.

Image Credit: Photos.com

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