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Do physicians really believe in placebos?

ResearchBlogging.orgIn a previous post, I argued that placebo is an artifact of certain clinical interactions, rather than a treatment that we can exploit. Apparently, there are a whole lot of doctors out there who don’t agree with me. Or are there?

A recent study published in the British Medical Journal is getting
a lot of enk (e-ink) in the blogosphere. As a practicing internist, I have some pretty strong opinions (based in fact, of course) about both this study and placebos in general.

The Study

The current BMJ study defines placebo as “positive clinical outcomes caused by a treatment that is not attributable to its known physical properties or mechanism of action.”  I’ve got a lot of problems with this definition, but we’ll get to that later.  It also allowed physiologically active medications to “count” as placebos.  Oops.

The study surveyed internists and rheumatologists practicing in the U.S. They tried to control negative responses to the term “placebo” thusly (from the Methods section):

Because the term “placebo” and behaviours surrounding its use can be contentious, we devised a series of non-judgmental questions beginning with broad questions that avoided the term “placebo” and then gradually gained more specificity, culminating in items whose responses used a clear definition of a “placebo treatment.” By constructing a series of items in this manner we allowed respondents to describe their attitudes and experiences as accurately as possible.

The first set of three items began with a hypothetical scenario in which a dextrose tablet was shown in clinical trials to be superior to a no treatment control group (thus establishing its efficacy as a placebo treatment). To avoid biasing responses these three questions did not use the term “placebo,” “placebo treatment,” or “placebo effect.”

I know a lot of doctors.  They tend to be fairly bright.  I don’t think any of them would be deceived by this scenario.  When you read “dextrose pill”, you think “placebo”.  It might as well be the same word.

Respondents were then asked to indicate which of several treatments they had used within the past year primarily as a placebo treatment, defined as a treatment whose benefits derive from positive patient expectations and not from the physiological mechanism of the treatment itself; and how they typically described placebo treatments to patients. By asking these five questions both without the term “placebo” and then using the term, we aimed to assess physicians’ practices as accurately as possible.

All docs would recognize this as a placebo scenario.  However, the definition above is rather problematic.   Is a placebo “a treatment whose benefits derive from positive patient expectations and not from the physiologic mechanism of the treatment itself”?

The validity of this study hinges on the answer to this question.

Placebo—I do not think it means what you think it means

The concept of placebo, and the way it is used in this study are both problematic.  First, we have an elephant in the exam room.  When we observe a so-called placebo effect, we are very susceptible to the post hoc ergo propter hoc fallacy.  Just because the patient’s condition changes doesn’t mean we have done anything to cause that change.  In fact, due to the remarkably inexact human pattern-recognition software, we are likely to attribute a change in a patient’s condition to something, and if we don’t know what that something is, we may label it “placebo”.  So the very concept of placebo may be an artifact of our way of thinking, a label to place on a co-incidence, rather than a “thing”.  We may have wrongly reified a rather fuzzy concept.


Posted in: Science and Medicine

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When compassion is outshined by ignorance

In a media-saturated society, public figures have a disproportionate influence on people’s understanding of science and medicine. Most patients see their doctor no more than a couple of times a year, but they watch TV, go online, or read a paper daily. In our newspapers and in our news rooms, dedicated science reporters are becoming vanishingly rare.   A wide range of news sources seep into this gap, but perhaps one of the most unfortunate is the “celebrity health expert”.

Uninformed statements from celebrities are nothing new, but when the queen of the antivaccination movement gets to call someone else stupid, that’s news.

Comedian Dennis Leary did little to advance the cause of humor or medical knowledge when he wrote this:

“There is a huge boom in autism right now because inattentive mothers and competitive dads want an explanation for why their dumb-ass kids can’t compete academically, so they throw money into the happy laps of shrinks . . . to get back diagnoses that help explain away the deficiencies of their junior morons. I don’t give a [bleep] what these crackerjack whack jobs tell you – yer kid is NOT autistic. He’s just stupid. Or lazy. Or both.”

There is no “autism epidemic” as such, but there sure is a lot of ink spilled in ignorance, and Leary certainly seems to have a surfeit of that.  But never fear, Jenny McCarthy will come to the rescue of autistic folks everywhere.

“My fight isn’t with Denis Leary, my fight is with the government — a bigger fish to fry. So I’m still gonna work on the vaccines and I’m still working on pediatricians and Denis Leary can go hopefully be more educated by every mother that stops him from this day forward to give him a piece of their mind,” she said.


Posted in: Science and the Media, Vaccines

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Is there no end to unscientific treatments for autism?

OK, it’s true that I’m only scheduled to post every other week or so, but I couldn’t resist sharing this one with you (which I’ve cross-posted over at denialism blog).  I promise to get back to my assigned schedule after this one.  Thanks for your indulgence.  –PalMD

If you’ve been a regular reader of SBM or denialism blog, you know that plausibility plays an important part in science-based medicine.  If plausibility is discounted, clinical studies of improbable medical claims can show apparently positive results.  But once pre-test probability is factored in, the truth is revealed—magic water can’t treat disease, no matter what a particular study may say.  So it was with great dismay that I read an email from a reader telling me about parents buying hyperbaric chambers for their autistic children.  Let’s review some science.

In Breathing 101, we talked about how the oxygen delivered to your lungs depends on both the percentage of oxygen in the air, and the air pressure.  We looked at how diminishing atmospheric pressure, for example at altitude, makes it harder to breathe.

Of course it is also possible to expose people to increased atmospheric pressure, which has therapeutic uses in the form of hyperbaric oxygen therapy (HBOT).

Oxygen delivery to tissue depends on several factors.  We already talked about the air itself.  Once air gets enters the lungs, most of the oxygen transported to your tissues is carried by the hemoglobin molecules in your red blood cells (under normal conditions).  A small amount is directly dissolved in the blood.  The amount dissolved in the blood is dependent on (no surprise) the percentage of oxygen and the atmospheric pressure.  By increasing the atmospheric pressure from 1 atm (760 torr) to 3 atm, the amount of oxygen dissolved in the blood is enough to meet your body’s needs independent of heme-associated oxygen.

This is a good thing.

Posted in: Neuroscience/Mental Health, Science and Medicine

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Fake diseases, false compassion

Hi,  everybody!  I’m PalMD (although my byline says differently), and you may remember me from such other blogs as WhiteCoat Underground and denialism. The folks around here were kind enough to give me a regular gig dispensing my brand of medical information transfer, and I’m going to start out with a basic question: what is a disease?

Human beings have some pretty powerful pattern-recognition software—so powerful that it can over-perceive patterns, sometimes causing us to confuse randomness for order.  This impacts all aspects of human thought, including medicine.

In the realm of medicine, we define disease as alterations in physiology, anatomy, biochemistry, etc. that causes significant discomfort, disability, or increased risk for same.  OK, really, I sort of cobbled that together, but you get the idea — a disease is a definable alteration in normal function.  A corollary to this is that to define a disease, we must know something about what is normal (a discussion for another time).  A related term is syndrome, which we usually define as  “a set of signs or a series of events occurring together that often point to a single disease or condition as the cause.”  What this effectively means is that we use the word “syndrome” to indicate a set of abnormal findings without a clear cause, and “disease” to indicate the abnormal findings with a putative cause.

(All this verbosity is leading somewhere—I promise.)

“Syndrome” is sometimes a useful place-holder term for a nascent disease.  Sometimes, however, a set of signs and symptoms is simply coincidence that we erroneously recognize as a pattern.

In popular culture there’s a lot of talk about “overmedicalization”, that is, calling things abnormal that are simply slight variations in the wide range of human health.   You’ll find people who argue that treating ADHD with medications is tantamount to abuse (and lost in the hysteria is the real possibility that we are over-medicating some kids). You’ll also find groups that argue that deafness or autism are simply “other”, but not “abnormal” as such.  This, of course, is wrong.  While a deaf or autistic person is just as valuable as a “normal”, and may have just as much to contribute to society, they are very far from normal human health.

And now you have the proper background to approach the problem of fake diseases.


Posted in: Science and Medicine

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