The Power of the Placebo (Part 2 of 2)

Continued from Part 1

While the placebo effect is an acknowledged part of modern medicine (and the driving force behind most alternative medical treatments), the power of the placebo continues to influence how many patients respond to treatment.    As patients and doctors alike believe that a treatment will work, patients tend to recover faster than they might do otherwise.   When a newer (and more expensive) drug comes out however, the drug it replaces often performs less well in research because doctors are less confident in helping patients.   Research has shown that simply changing the size and colour of a pill can be enough to change its apparent effectiveness. 

But how exactly does the placebo effect work?   Research into using placebos for pain  suggests that increased endorphin levels and reduced cholecystokinin production in the brain may lead to placebo-induced pain relief.    A 1978 study showed that the opioid antagonist naloxone can block endorphins and prevent the placebo effect from occurring.   These results only appear to apply to pain relief however.  

Placebos have been shown to be effective in relieving a wide range of symptoms and the power of belief can also play a role in worsening symptoms as well.   Much like the placebo effect, nocebos (coming from the Latin phrase for "I will harm") can have a powerful effect on health by making many medical conditions worse and may even play a role in "voodoo deaths" linked to curses.   Various proposed explanations for the placebo (and nocebo) effect include suggestion,  operant and classical conditioning, cognitive dissonance, the Hawthorne effect, and expectancy effects though they are all largely based on speculation.  All that we can say  for certain is that the exact mechanism for the placebo effect is (still) unknown.

Is there such a thing as a placebo-responder personality?   While some researchers have attempted to link patient responding to placebos to suggestibility or other personality traits, the  results have been largely inconclusive.   In studies observing how subjects respond to placebos over multiple trials, no consistent pattern has been identified.   In other words,  the same subjects who respond to placebos in one trial may not respond in later trials or vice versa.    It is also difficult to decide exactly what the placebo effect can affect.   Though most research into placebo use focuses on pain relief,  some studies suggest that belief in placebos can accomplish much more, including relieving swelling and changing serum cortisol levels.     The extent to which the placebo effect can relieve symptoms can range from no effect at all to total relief in some cases.

In identifying the different factors that can make placebos effective, researchers have identified the following:

  • The nature of the intervention - the more intrusive the intervention, the more effective the placebo effect seems to be.  "Sham surgery" (skin incisions without an actual operation) seems to be at least partially effective in relieving symptoms for most patients receiving it.     Placebo injections also appear more effective than placebo pills.   the more discomfort associated with the sham treatment, the better.    Treatments that are more "exotic", i.e., involving complicated technology or a radical new medical technique also seems to increase the effectiveness of the placebo.
  • The credibility of the one providing the treatment -  Doctors with a high degree of status showing strong belief in their treatment are more likely to have a positive effect on their patients.   Also, therapists showing warmth and empathy to their patients will get better results on average.
  • Patient expectation -  If the patient is involved in the treatment and has developed a sense of trust in the doctor and the treatment being received, the placebo effect is likely to be stronger.
  • The nature of the complaint - Though most placebo research has focused on pain relief, a wide range of other symptoms appear to be affected by belief as well.   Biofeedback research suggests that many physiological functions can be consciously controlled although it is still unknown whether some complaints or disorders may be more "placebo prone" than others.
  • The treatment setting -  A 1994 clinical study found that therapeutic setting was the only significant predictor for nocebo effects, i.e., patients in some clinical centres were more likely to experience adverse reactions to a placebo than patients in other centres.   This suggests that even the location where treatment is received may play a role in whether the placebo effect occurs.

It is also important to understand that simply observing patients improving after taking a placebo cannot be considered evidence for a placebo effect at work.    According to Edward Ernst and his colleagues,  evidence for a "true placebo effect" needs to rule out other factors that might be contributing to patients getting better.    This can include natural recovery from illness, regression towards the mean,  patient bias, or other time-related factors that researchers failed to take into account.    In other words, simply seeing a patient improve does not mean that a placebo effect is occuring although  this "perceived placebo effect" is often confused with the real effect.    To make medical research even more complicated, proving that a treatment is really effective means showing that the positive benefits are greater than what could be accounted for by the true and perceived placebo effects. 

In a real sense, the placebo effect is a part of all medical treatments, whether intended or not.  Many of the factors that make the placebo effect more powerful are also used by caring health professionals to reassure patients and make them more confident that the treatment will be effective.   That same confidence also plays a role in the perceived benefits that patients being treated with alternative medicine often experience and which, in turn, are taken as "proof" of their effectiveness.   Virtually every practitioner of alternative medicine can produce anecdotes provided by apparently grateful clients.   Though these glowing anecdotes can seem convincing to people desperate for a cure,  there are always limits to what can be accomplished by belief alone. 

While there are certainly colourful stories of the placebo effect at work (including the ones mentioned in Part One),  relying on placebos to treat patients often invokes a critical problem in medical ethics.  Is it permissible for doctors to lie to their patients, even in a good cause?  And can practitioners of alternative medicine be considered to be providing a valuable service to patients if the placebo effect makes the treatment more effective than it might otherwise be?  

There are still too many unanswered questions about how and why placebos work despite the enormous amount of research that has been done to date.   Though the placebo effect has a long and venerable history, it remains a mystery in many ways.   And perhaps it always will be.













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