On Wed, Jan 14, 2015 at 10:18 AM, Quentin Anciaux <allco...@gmail.com> wrote:
> Question is then how do you test if a medication works or not if not by > correlation between those that take the medication and are better than > those who don't? > You conduct a randomized trial where you compel one random group to take it and another not to, such that you control one variable (taking/not taking the drug). If you don't control the experiment in this way, you can't differentiate which is the correct causal relation is correct concerning the Drug Use (D) and Effect (E), and a separate cause (S). Is it: 1. D -> E 2. E -> D 3. S -> E and S -> D All three of the above scenarios will result in an observed correlation, but in only one of them is it true that not using the drug will reduce the presence of the effect. > If it's not what you imply, what makes you think those studies don't use > a comparison group of people who don't use cannabis? because if they didn't > did that they'll only point out a correlation and I would agree with you it > means nothing per se. > The reason I doubt a controlled study was performed is because it is illegal and essentially banned even for research purposes. It's far easier, and less legally questionable to study existing users and compare them to others who habitually don't. But this can't differentiate from case (2) or case (3) above. In such studies there's the notion of "compliers", they are people who try to follow all the health device they're given, they exercise, floss regularly, don't smoke, or drink excessively, don't do drugs, etc. However the presence of compliers represents a huge confounding factor in all kinds of studies, because even the belief in "drugs are bad for you" will (on account of these compliers) become intercorrelated with all kinds of other things compliers do. So if exercise helps with depression, and compliers both exercise and don't do drugs, now you may be mislead into thinking drug uses causes depression, when really it would be that exercise reduces it. There was one study I saw published that sound flossing reduces heart diease. Does it really, or might it be one of these compliance-related correlations? We won't know unless we force one large group to floss and another large group not to for a significant period of time and see how many develop heart disease. > So I took ypur comment as dismissing without any other reason than wanting > to dismiss. > I did not mean to come off that way. Thanks for understanding. Jason > Le 14 janv. 2015 16:51, "Jason Resch" <jasonre...@gmail.com> a écrit : > >> >> >> On Wed, Jan 14, 2015 at 9:22 AM, Quentin Anciaux <allco...@gmail.com> >> wrote: >> >>> >>> >>> 2015-01-14 16:16 GMT+01:00 Jason Resch <jasonre...@gmail.com>: >>> >>>> >>>> >>>> On Wed, Jan 14, 2015 at 9:02 AM, Quentin Anciaux <allco...@gmail.com> >>>> wrote: >>>> >>>>> >>>>> >>>>> 2015-01-14 15:39 GMT+01:00 Jason Resch <jasonre...@gmail.com>: >>>>> >>>>>> >>>>>> >>>>>> Correlations don't prove causal relations, >>>>>> >>>>> >>>>> >>>>> I know all I point out, is that there are now many study done on that >>>>> correlation... You can dismiss them.. >>>>> >>>> >>>> My point is that correlations themselves (even when proven) are >>>> effectively meaningless. Take the supposed evidence that nutritionists used >>>> to demonize fat as leading to heart attacks. Correlations where shown >>>> between various countries that showed countries with higher fat intake had >>>> higher incidence of heart disease. But it was later shown that fat intake >>>> in countries was determined largely by the countries per capita GDP. So now >>>> you can see the correlational study (which put the blame on fat) could be >>>> explained by anything else that correlates with per capita GDP: stress, >>>> long working house, consumption of sugar, cigarette use, etc. >>>> >>>> Think of it this way: if heart attacks correlate with economic >>>> development of a country, another study might have been able to show a >>>> strong correlation between driving cars and heart attacks (because more >>>> cars are owned and more people drive in those countries). But it would have >>>> almost certainly been wrong to conclude "Drive less to avoid heart >>>> disease". Yet this is the same error that led nutritionists to the bad >>>> advice of "Eat less fat to avoid heart disease". Only a controlled study >>>> which actually tests the hypothesis can separate mere correlations and true >>>> causes. Do we know if cannabis correlates with depression because depressed >>>> people seek it to self-medicate? We might observe a similar correlation >>>> between depression and SSRI use, but we know SSRIs are used to treat >>>> depression, so it makes sense. We don't conclude though that SSRIs cause >>>> depression. >>>> >>>> If your claim is that cannabis causes depression, you need to point to >>>> a study that takes two groups of subjects, subjects one group's members to >>>> regular cannabis use and another that prohibits cannabis use among members, >>>> and then study whether the incidence of depression is higher in one group >>>> vs. the other. All science is based on "Observe, Form Theory, Test Theory". >>>> It's important that we realize all correlation studies (in all domains) are >>>> nothing but the first step "Observe". Forming policies or opinions from >>>> formed theories that haven't been tested is asking for trouble. (Just look >>>> at the current US and now world health crisis due to moving people to >>>> low-fat diets when the only basis was a correlational study (since >>>> disproved by controlled testing)). >>>> >>>> >>>>> yet they exists and they seems correctly done... maybe it's >>>>> prohibitionist agenda.. I know for myself that I can't control my cannabis >>>>> usage and when I was using, I was abusing and that certainly did not help >>>>> me at that time... But if you think cannabis abuse is a fairy tale... fine >>>>> with me... and if you think it is not, but it has absolutely no side >>>>> effect... ok... I won't agree with you but it's your belief... and I've >>>>> mine. >>>>> >>>> >>>> I don't see where are you getting this from out of what I said. >>>> >>>> >>> I'm getting at that you don't know the various studies, but you know >>> they are bad, and only point out correlation without anything else... well, >>> you can be bad faith and absolutely sure cannabis is absolutely safe... ok >>> then... but can I ask you studies that shows that too ? >>> >>> >> >> I said nothing either for or against cannabis use. I only cautioned that >> correlational studies cannot be used to draw conclusions ever, in any >> domain of inquriy. That's the only point I wanted to make. (I'll retreat >> back into the dark now) >> >> Jason >> >> -- >> You received this message because you are subscribed to the Google Groups >> "Everything List" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to everything-list+unsubscr...@googlegroups.com. >> To post to this group, send email to everything-list@googlegroups.com. >> Visit this group at http://groups.google.com/group/everything-list. >> For more options, visit https://groups.google.com/d/optout. >> > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-list+unsubscr...@googlegroups.com. > To post to this group, send email to everything-list@googlegroups.com. > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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