Salama:  

Randomized controlled trials (RCT's) are the most convincing form of medical
evidence.  RCT's can be done where the question is susceptible to an RCT and
where sufficient resources exist to perform an RCT.

A randomized controlled trial of smoking and lung cancer is ethically
impossible, since overwhelming evidence from other scientific studies shows
that lung cancer is caused by smoking.  This causal relationship has been
accepted by every independent scientist I know, since at least sometime in
the 1970's.

There is also no randomized controlled trial, at least known to me, showing
that HIV causes AIDS.  If such a trial were someday undertaken, would you
volunteer to be one of the research subjects?

A randomized controlled trial of most social determinants of health (SDOH)
is also ethically and practically impossible.  That doesn't mean SDOH aren't
important!  But it means that they must be studied by other methods, which
individually are less certain than most RCT's but which can combine to
produce a scientifically compelling picture.

For discussion of the strengths of non-RCT evidence, and the potential for
error in RCT's, please consult a good graduate-level epidemiology text.

Best wishes!

Dave Cundiff, MD, MPH
Olympia, Washington, USA

***

On 3/10/07 9:48 PM, "Salama Habshi" <[log in to unmask]> wrote:

> I have a question Is it ethically accepted to say that Lung cancer is caused
> by smoking although there is no enough evidence (expriemental Randomized
> Controledl Trial RCT) to support this hypothesis.
> 
> Regards,
> Salama
> 
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