Tag Archives: evidence based medicine

What is science? Is medicine and biology science? Let’s discuss

A regular commenter took off on the Economics is not a science discussion to suggest Medicine and Biology are not science. My answer below is, Sometimes and It Depends.


Much of medical and biological studies are observational and not do not qualify as science either.

Commenter says–It’s mostly just conjecture. “Well I suppose” leads to “maybe”. Not science.

People are talking about the movie “The Martian” and the phrase in there about “science the poop out of it” or something like that. Not science. Hard work, observation and engineering. In my dad’s day they knew the difference between science and engineering. Now anything even remotely technical is “science”.

Disagree with your dictionary definition. “3. any of the branches of natural or physical science.” Especially not. Also, “4. systematized knowledge in general”. Not. It’s science because it’s systematized? Huh? My grandkids legos are systematized in little bins but it’s NOT science. Good grief.

So, my turn.

In medicine we like the term evidence based and that means repeat, rinse, repeat and test your hypothesis against the evidence, that’s the critical scientific methodology.

In the complex world of biological structure and function, much of which is still not understood, there are lots of opportunities to to be wrong. Miss a confounder and your hypothesis is an empty one.

Good examples of biological science in action–Koch’s postulates for proving the cause of a disease, with particular emphasis on infectious diseases.

Another scientific method is the Bradford Hill rules on proving causation, for example beneficial or toxic effect, which look a lot like the Koch postulates for chemicals or physical effects on living organisms.

The Koch postulates can be used to disprove a cause of a infectious disease and modified to provide knowledge of non infectious diseases.

The Bradford Hill rules can be used to prove or disprove a toxic or beneficial effect of an exposure to a physical or chemical agent or condition. .

Koch’s postulates are the following:

1. The microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms.
2. The microorganism must be isolated from a diseased organism and grown in pure culture.
3. The cultured microorganism should cause disease when introduced into a healthy organism.
4. The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent.

The Bradford Hill Rules can be turned for positive and negative evidence of effect, toxic or benificial.

The Bradford Hill Rules, from Wiki:

The Bradford Hill criteria for causation are a group of minimal conditions necessary to provide adequate evidence of a causal relationship between an incidence and a possible consequence, established by the English epidemiologist Sir Austin Bradford Hill (1897–1991) in 1965.

The list of the criteria is as follows:

1 Strength (effect size): 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 (reproducibility): Consistent findings observed by different persons in different places with different samples strengthens the likelihood of an effect.
3 Specificity: Causation is likely if there is 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.
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”.
Analogy: The effect of similar factors may be considered.

So, if you are honest about testing the postulates and the rules–you can produce reliable, reproducible explanations or you can prove up your hypothesis as valid. That’s evidence based science. You can’t cherry pick the rules however for the ones that work to prove your hypothesis. They come as a unit, and exceptions to the proof are less scientifically reliable. There are some exceptions, for example the organism sometimes are hard to culture in the case of Koch’s postulates.

A modification of the Koch’s postulates can provide diagnostic criteria for diseases that are not infectious.

If you hold to the rules, you can test a hypothesis, and in fact infectious disease, diagnostic nosology, pharmacology and toxicology can be made scientific.

Medicine is only science if it is scientific and evidence based–otherwise it may or may not be right based on observational anecdotal information or “fly by the seat of your experience or the experience of others,” but it is not scientific, evidence based medicine unless it is reproducible and falsifiable. When I say testable and reliably reproducible, that covers the Popper requirement that it be falsifiable.

An example of an organized effort to produce evidence based medicine is the Cochran Project that is devoted to gathering reliable medical research and identifying unreliable research.


Simple examples of the problem of reliable science in medicine is the confounder of an unknown or even known–some genetic unknown or the known problem of placebo effect. So that’s why when medicine gets serious it does Randomized Controlled studies that are blinded and placebo controlled to test drug effects.

In the case of the second inquiry–biology, the scientific knowledge of living things requires the use of chemistry, physics, and observational disciplines like anatomy and functional anatomy to determine both complex and not so complex functions of living things. Biology can begin with cold cuts, microscopic studies and chemical analysis to achieve reliable knowledge, but when we go to complex functionalities it gets harder.

One example is that at the cellular level anatomy and chemical functionality are not simple–they are as complex for the one-celled as the much more complex organism. No simple way to make DNA reproduce or membranes function properly, so bacteria have the same cellular complexities as the cell of an elephant or a human.


Sensible Medicine Discussion

Gorski provides insight and analysis on evidence based medicine, that might promote better medical decision making, even reduce waste and unnecessary even risky procedures or treatments.

I liked it.