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my 2 cents: 

Bradford-Hill is one reference list I always refer too even if via a RCT. yet 
Hill cautioned 

"None of my nine viewpoints can bring indisputable evidence for or against the 
cause-and-effect hypothesis and none can be required sine qua non". 

This point is key and maybe one can argue that it seems based on the evidence 
(if you feel strongly enough that your results point to causation) that 'a 
causal association seems to exist, based on a balance of probability'.....I dont 
think one can say 100%....we are always operating in the realm of probability in 
this area...


	1. Strength: A small association does not mean that there is not a causal 
effect, though the larger the association, the more likely that it is causal.
	2. Consistency: Consistent findings observed by different persons in different 
places with different samples strengthens the likelihood of an effect.
	3. Specificity: Causation is likely if a very specific population at a specific 
site and disease with no other likely explanation. The more specific an 
association between a factor and an effect is, the bigger the probability of a 
causal relationship.[12]
	4. Temporality: The effect has to occur after the cause (and if there is an 
expected delay between the cause and expected effect, then the effect must occur 
after that delay).
	5. Biological gradient: Greater exposure should generally lead to greater 
incidence of the effect. However, in some cases, the mere presence of the factor 
can trigger the effect. In other cases, an inverse proportion is observed: 
greater exposure leads to lower incidence.
	6. Plausibility: A plausible mechanism between cause and effect is helpful (but 
Hill noted that knowledge of the mechanism is limited by current knowledge).
	7. Coherence: Coherence between epidemiological and laboratory findings 
increases the likelihood of an effect. However, Hill noted that "... lack of 
such [laboratory] evidence cannot nullify the epidemiological effect on 
associations".
	8. Experiment: "Occasionally it is possible to appeal to experimental 
evidence".
	9. Analogy: The effect of similar factors may be considered.
 
 
 
 
 
 
Best,

Paul E. Alexander
 





________________________________
From: "Djulbegovic, Benjamin" <[log in to unmask]>
To: [log in to unmask]
Sent: Fri, January 28, 2011 10:06:33 AM
Subject: Can RCT help establish causation?


Dear all
I'd like to post this question to the group that I have been thinking about for 
some time... Is there a scientific method that allows us to LOGICALLY 
 distinguish the cause-effect from the coincidence? David Hume, one of the most 
influential philosophers of all times, concluded that there is no such a 
 method. This was before RCTs were "invented". Many people have made cogent 
arguments that (a well done) RCT is the ONLY method that can allow us to draw 
the inferences about causation. Because this is not possible in the 
observational studies, RCTs are considered (all other things being equal) to 
provide more credible evidence than non-RCTs. However, some philosophers have 
challenged this supposedly unique feature of RCT- they claim that RCTs  cannot 
(on theoretical and logical ground) establish the relationship between the cause 
and effect any better than non-RCTs. I would appreciate some thoughts from the 
group:
1. Can RCT distinguish between the cause and effect vs. coincidences? (under 
which -theoretical- conditions?) 
If the answer is "no", is there any other method that can help establish the 
cause and effect relationship?
I believe the answer to this question is of profound relevance to EBM.

Thanks 
 Ben Djulbegovic 

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