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Hi, I have been wondering the last week or so regarding the placebo effect. There is lots of material where they talk of the 30% or so of unwarranted improvement people get on sham treatments (ie the placebo arm of studies).

What I have yet to read is about people on the actual treatment who *lose* 30% effectiveness due to the same effect? ie The placebo effect working in reverse. Logically, I would expect it to work both ways.

I haven't heard of this either, although it seems logical to assume it happens.
It is similar, though not identical to, the "nocebo" effect, where a patient who receives placebo but really believes he or she is taking a drug with side effects, will actually experience some of those side effects.
The word is beginning to be used in a completely different way: to describe a drug which genuinely has an action and also has unpleasant effects as having nocebo effect.

What you are saying though is very interesting and extremely relevant to trials: that if you are actually receiving the therapeutic agent, but strongly believe you're getting the placebo, the results could be skewed. It would be interesting to find out if this is taken into account.

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TwistedHelix wrote:It would be interesting to find out if this is taken into account.

I have yet to see it taken into account. Most maths that I have seen are basically: A-B where A is the result on actual treatment and B is the result on the placebo arm. There is no addition back in for possible degradation of the actual treatment arm results.

Bob, I did a search, and could not find any actual thread on the "reverse placebo effect". All I found were side comments to it within Tovaxin specific threads of people guessing which arm they are in; about 6 months ago.

Not that this is relevant but the private neurologist who diagnosed me said that the 30% reduction in relapse rates from beta interferon was akin to a placebo affect. I haven't read that anywhere else but I think one's ability to delude oneself is very powerful in either direction. I started out on the antibiotics very optimistic and believing that they were having an effect and now I'm probably erring on the flip side of the coin!

gibbledygook wrote:I started out on the antibiotics very optimistic and believing that they were having an effect and now I'm probably erring on the flip side of the coin!

I would be guessing in that you started with doxy and roxy. Doxy (and mino) ARE providing some possible positive results in small trials.

gibbledygook wrote:Not that this is relevant but the private neurologist who diagnosed me said that the 30% reduction in relapse rates from beta interferon was akin to a placebo affect.

It might be if there was no placebo control group. However, I believe that this number quoted for Ifn-B's effectiveness is that compared to placebo. In effect, a 30% reduction in the progression of disability when compared to the placebo group.

The data isn't very impressive, but here's a plot from the Dr's Prescribing Information literature for Avonex.



Still, one of the problems with Ifn-B is that the side effects can be rather severe in some individuals. It wouldn't be too difficult for folks in a placebo group to figure out that they weren't getting the real thing. Unless, of course, Biogen was deliberately giving those on placebo a 24 hour flu but then there would hopefully be ethical constraints against such actions. Still, I have read of studies where people in the placebo group have dropped out of a particular study due to the side effects. Now that's some powerful placebo!

NHE