Causation Just Seems To Get Harder and Harder
See for example:
The hygiene hypothesis does not mean that you should expose your kids to pathogens.
Genes + nitrosamines + helicobacter pylori = pancreatic cancer?
Drinking and smoking does lead to head and neck cancers; but not in the sense that you mean.
and,
Parvovirus B19 infection in children may not be so benign after all; it may be the first step on the path to childhood leukemia
But always remember, correlation does establish causation. Sal Khan explains it in Correlation and Causation.
