PE. Thanks. Maybe just goes to show how something that may have had a very limited link with an actual happening which itself was then taken out of context becomes to be quoted as fact but is a myth.
The problem is always that it may have occurred a few times but be due to other factors and a spurious correlation is made.
In matters much more vital such as medicines one can begin to appreciate why randomised control trials involving 1000s are conducted before any meaningful conclusions are drawn.