You raise a great point, but consider a different viewpoint. epidemiological studies are based on complex systems, systems with many variables and non-linearit

You raise a great point, but consider a different viewpoint. epidemiological studies are based on complex systems, systems with many variables and non-linearities. Atoms are a lot simpler (ha!) Here's what I think is going on: a hot paper comes out, presenting an interesting theory. People either like or don't like the theory based on preconceived notions, look at their data, plot every permutation of Xi versus Xj and publish the "juiciest plot." Ok, it sounds like I'm saying that the "scientific method" has broken down. I'm not, the preconceived notion is subtle, difficult, and hard to eradicate! So, people aren't starting with simple and building up. Not because they don't want to, but because they can't.