There is a very funny article about the limitations of Evidence Based Medicine in that radical periodical the British Medical Journal. It is an examination of the evidence for the use of parachutes.One of the many highlights:

The parachute and the healthy cohort effect
One of the major weaknesses of observational data is
the possibility of bias, including selection bias and
reporting bias, which can be obviated largely by using
randomised controlled trials. The relevance to
parachute use is that individuals jumping from aircraft
without the help of a parachute are likely to have a
high prevalence of pre-existing psychiatric morbidity.
Individuals who use parachutes are likely to have less
psychiatric morbidity and may also differ in key demographic
factors, such as income and cigarette use. It
follows, therefore, that the apparent protective effect of
parachutes may be merely an example of the “healthy
cohort” effect.

It’s very funny – a wonderful read. Enjoy!

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