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Understanding the Placebo Effect

The power of positive thinking takes on truly meaningful proportions as physicians and nurses learn to understand and respect the placebo effect.  The term placebo refers to a medical intervention that contains no active component, also called a “sham” procedure or pill.  A placebo medication is often composed of an inert substance, such as sugar. 


Far from being a trick on patients, placebos  can have a positive therapeutic effect on a wide variety of medical conditions, especially pain, hypertension and depression. This is known as the placebo effect.


Last month, my column described why and how academic centers like the University of Kentucky conduct clinical trials.  The placebo portion (or “arm”) of a clinical trial is a vital component that permits scientists to decide if a particular medicine, medical device or procedure is truly beneficial.  To be considered effective, a drug or procedure must prove to be significantly better than the placebo. 


The expectation of benefit in medicine is now known to be a compelling force. The placebo effect results in identifiable changes on images of nerve cell function in the brain known as functional MRI (fMRI) scans.  When patients receive placebo pills to treat a painful condition, for example, areas in the brain that are active in killing pain "light up" on the scan. Placebo analgesia is the result of the release of the brain’s own natural painkillers called endogenous opioids. Pain truly is “in your head,” and pain-killing responses to placebo can produce as strong a response as real analgesic medications in up to 40 percent of people.  Another upside to placebos:  as inert substances, they generally have no harmful side effects.


In clinical practice, placebo pills are rarely used in treatment plans. But our bodies regularly experience the placebo response in everyday life.  For example, if you approach an uneven step where you once tripped, you’ll likely experience a quickened pulse and heightened alertness, even though there is currently no imminent danger.  This is our brain’s “flight and fight” response, and it’s a natural physiologic reaction to anticipation or remembrance of an event. 


Similarly, if you are given a pill your doctor calls a “stimulant,” your heart rate and blood pressure will increase; whereas if the same pill is called a “sedative,” you’ll likely experience sleepiness.  The power of expectation is ubiquitous, and doctors are not immune to it.  Once, when I was competing on the cross country course at the Kentucky Horse park, the very same fence was labeled “The Coffin” for one group of riders and “Baby’s Breath” for another.  Not surprisingly, there were more refusals and lost points at The Coffin.


One of my current clinical trials at UK, conducted with Dr. John Gurley in Cardiology, involves implanting a closure device for a small hole in the heart to determine if such closure will improve migraine headaches.  To be sure that just having the procedure by itself doesn’t influence the number or severity of headaches people experience, a simulation is performed for some of the patients. It is done in the same room, with the same treatment routine, with most of the health care personnel (and the patient) “blinded” to whether the patient receives or does not receive the device.  Only after the study is completed, after several years, will the results be “unblinded,” and the researchers and patients know who truly received the device. 


Such an intricate trial gives us renewed respect for the processes that are needed to truly differentiate successful treatment from the very real, very powerful effect of the placebo.


Dr. Tarvez Tucker is an associate professor of neurology in the University of Kentucky College of Medicine and director of the UK HealthCare Headache and Pain Clinic.