He Said/She Said - Causation vs. Correlation: How Medical Studies work!

Typically, in the Medical Issues & Conspiracies forum, evidence is brought forth in a recognizable pattern. It will start inevitably with anecdotal evidence, a single or series of instances of which lead one to a hypothesis associating variables with causality; however, this association does not prove causality. Unfortunately, many members, or the general public for that matter, take their own experience as proof positive, regardless of conflicting data, no matter how convincing they may be.

Since the majority of our members have enough intelligence to realize the inadequacies of this anecdotal, often referred to as circumstantial, evidence, it is either dismissed or the poster is asked to provide further "sources" or evidence to support their experiences. Confusion and frustration ensues.

The supporting poster searches google, finds a study, or article written about a study, posts it, and combining their anecdotal evidence with their newly found study they proclaim definitive proof of their hypothesis, blindly and ignorantly.

Along comes the apposing poster with not only a study supporting his opposition but also one that shows different variables and, ultimately, different causality. Next comes 4 pages of bickering while both sides attempt to defend their own position, derailing the other simultaneously.

The result? Both slowly lose willingness to debate. Each poster holds his evidence as definitive and obvious while mentally declaring victory over a foe whom is unwilling to accept the facts and has an obvious agenda. But no, it's not over. The debate, if you call it that, is merely idle, waiting for the next thread to reunite the newly formed enemies in what will inevitably be a life long battle on ATS. Respected Foes, as we call them. Yet, respect is usually hidden behind the personal attacks and insults, that is.

Many times these arguments, which provide studies suggesting one cause and yet even more studies suggesting the exact opposite, often times leads to this statement by many posters: "The medical establishment has no idea what they're doing. I don't think they have any clue as to what's causing these diseases. We've gone from being able to eat eggs, to having to avoid them completely, to avoiding the yolk and now they're a whole health food again."

So, in an attempt to mitigate these debates, the following is a list of the different types of medical evidence/medical studies, how their designed and what they tell us.

Obeservational/Epidemiological:

Correlation does not imply causation. These are the types of studies that have most people confused as to what causes certain ailments. It's important to understand that observational/epidemiological studies should be used to form hypotheses, not pin-point causality. Despite what an article in the NY Times has written, if a study has inferred correlation/association, it has proved nothing.

Anecdotal Evidence: casual observations or indications rather than rigorous or scientific analysis. These are in most cases non-scientific.

Case Series and Case Studies: These are reviewed reports on individual cases or a series of similar cases. Typically, these are unusual or rare cases that are used to illustrate an aspect or treatment of a condition.

Case-Control Study:
Case-control studies are used to identify factors that may contribute to a medical condition by comparing subjects who have that condition (the 'cases') with patients who do not have the condition but are otherwise similar (the 'controls'). They are designed to estimate the odds of developing a certain disease or condition. They determine association between condition and risk factor. They are rated as low quality, grade 3, on a standard scale of medical evidence. See www.bmj.com...

Cohort/Longitudinal Study: These studies involve a case-defined population who have a certain treatment, or exposure, compared to a population that is non-treated, or unexposed. In medicine, a cohort study is often undertaken to obtain evidence to try to refute the existence of a suspected association between cause and effect; failure to refute a hypothesis strengthens confidence in it. See Framingham Heart Study

Cross Sectional Study: These are very similar to Cohort/Longitudinal Studies with the main difference being that Cross Sectional Studies focus on one point in time while Longitudinal Studies cover a population over a long period of time.

Just a few examples of the types of inferences that have been made by these types of studies:

Dog Tail-Chasing Linked to High Cholesterol

Shaving, Heart Disease and Stroke

Treatment Studies/Clinical Trials

These studies are much more effective at identifying cause, which is why they are often used to test the hypotheses of observational studies.

Randomized Controlled Studies: a study in which 1). There are two groups, one treatment group and one control group. The treatment group receives the treatment under investigation, and the control group receives either no treatment (placebo) or standard treatment. 2). Patients are randomly assigned to all groups.

These randomized trials can be performed in many ways:

Non-Blind Trial: a type of clinical trial in which both the researchers and participants know which treatment is being administered

Single Blind:In a single-blind experiment, the individual subjects do not know whether they are so-called "test" subjects or members of an "experimental control" group.

Double Blind:In a double-blind experiment, neither the individuals nor the researchers know who belongs to the control group and the experimental group. Only after all the data have been recorded (and in some cases, analyzed) do the researchers learn which individuals are which.

These studies provide what is known as the Gold Standard in medical research.

Analyses:

Meta-Analaysis: a meta-analysis combines the results of several studies that address a set of related research hypotheses.

Systemic-Analysis: A systematic review is a comprehensive survey of a topic that takes great care to find all relevant studies of the highest level of evidence, published and unpublished, assess each study, synthesize the findings from individual studies in an unbiased, explicit and reproducible way and present a balanced and impartial summary of the findings with due consideration of any flaws in the evidence.

So, next time you read an article about a study that "suggests" any implications, I suggest you find the actual study and make your own decision.

Sources:
Wikipedia
BioMed

-Dev

[edit on 16-7-2009 by DevolutionEvolvd]

Wonderful post, Dev. It's like taking my research methods course all over again, haha.

Thanks. I think most people falsely give the same credence to all studies that they find. It's unfortunate.

It's also important to examine an abstract to sniff out any assumptions that could have possibly been made.

Remember, media outlets undoubtedly are often times biased and most journalists have no idea how to interpret a study, much less understand how it was designed. This often leads to facts being twisted and the acceptance of misinformation and myths. Myths that are assumed to be true and are touted as irrefutable fact.

We have to minimize assumptions in science and must constantly be trying to disprove our hypotheses. This is the true scientific method. Sadly, it's rarely observed.

-Dev

Interesting thread, from the thread title and on first paragraph I was assuming it to be about the pyschological differences between men & women and their bickering.

But on further reading it's not and actually very informative.

Thanks for a good read!

reply to post by DevolutionEvolvd


edited to remove post.
Never mind.

[edit on 19-7-2009 by zazzafrazz]

is this how the sorry ###ssess work. you look thru your booklet that the insurance co. sends you for places and docs that fit your insurance only.you then finnally find one and you schedule an appoinment for which you cannot go to because it is an emergency. you then go to the doctor and give your insurance card which is based on how much you make in money. so if you have more money you get better insurance that gets elected for you, not by you, on the type of insurance you get, by how much you make and they give you selections, options of kinds of insurance you will get. this of coarse goes thru one person who recieves it and then thru another and this info gets sent back to you by another person who sends the billing info to you. meanwhile , you at the doc office, waits for a doc that can see you. you get there early, but you always wait. finally you go in. you then see a nurse, who then gives you a blood pressure reading and asks questions of your health. she leaves, you wait again. finally the doc arrives. he then asks you questions the nurse already asked you and a few more. the doc leaves, comes back in and gives you an answer after you had waited more. finally you can leave and wait more when you pick up your meds. meanwhile , back in the billing room your treatment goes to one person who files it , then to another who sends it to a biller and then to another who sends the bill to the insurance co. and the insurance co. recieves it thru a reciever , the reciever sends it to a filer and the filer sends it to the hospital biller and copies it , then hospital biller sends it to you in the mail. the drugs you get, the care you get, the hospital you get, the money you have,the insurance you have, all this and more go thru many hands before it gets back to you. why is this. why do we have to pay for all this b#s and lies and trickory of everyone. you know that if you go in for an ex-ray or a kat scan or anything else. the docs are not allowed by the insurance co to report if they find any other ailments that was not complained about. so , if you go in for a cold and they take an ex-ray and find cancer. you get treated for a cold and that is that. i hate insurance co. they all can go die somewhere.

reply to post by pudgeego


Weird. Paragraphs work, you know!

Thought this thread needed a BUMP!

-Dev