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
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.
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
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.
: 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 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
: 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
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:
a type of clinical trial in which both the researchers and participants know
which treatment is being administered
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.
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.
a meta-analysis combines the results of several studies that address a set of
related research hypotheses.
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.
[edit on 16-7-2009 by DevolutionEvolvd]