[LINK] Re: Double Blind Trials (Was to do with EMF)

rchirgwin at ozemail.com.au rchirgwin at ozemail.com.au
Fri Jan 12 18:32:06 AEDT 2007

Kim Holburn wrote:

> On 2007/Jan/12, at 12:25 AM, Stewart Fist wrote:
>> The reason why double blind trial are used, is not because of the  
>> placebo
>> effect, but because it is vitally important to rule out overt and  
>> covert
>> influence in recording the results by the investigator.
>> It is a problem of the 'witness' not the patient.  It is well known  
>> that
>> investigators who believe in the efficacy of a new drug will either
>> consciously/deliberately or unconsciously err on the side of recording
>> positive results.
>> Blind trials exist to stop this trend.
> I hadn't thought about it quite like that.  Do you think then, that  
> the placebo effect is just a virtual effect for the purposes of drug  
> testing and not something that's really happening at all?

It's more complex than that. "Placebo effect" is, anyway, a pop-culture 
shorthand for a complex phenomenon. Summarising this:
(sorry to those who object to WP)

1) Drug and placebo are equally ineffective
2) Drug is effective but has nasty side effects.
3) Drug is ineffective *and* has nasty side effects

1) Side effects are noticable before the drug's desired effect
2) Side effects are slower

So. What's perceived as a placebo effect may be:
- the placebo doesn't cause side-effects, so people using the placebo 
report feeling better than those using the active drug
- the subjects recognise that they're receiving a placebo (because of 
the lack of side effects), which effects how they report how they're feeling
- the subjects genuinely can't tell, in which case the outputs of the 
study can be trusted
...and so on.

Even in the double-blind test, the presence or absence of side-effects 
is a big marker to the recipient.

Because this all gets shorthanded, people believe that there's a simple 
something called the 'placebo effect' which everybody knows about and 
has been proved and measured and so on. It's no such thing; it's a 
debateable artefact of measurement which may reflect patient psychology, 
or may reflect the way drug tests are conducted, or ...


> Kim
> -- 
> Kim Holburn
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