I meant definitely proven with in a realistic sense. Smoke causes lung cancer, albeit only something like 20% of smokers get lung cancer. It's been proven, but not in the mathematical sense of the word.

One, a study with more than 32 people. Two, replications with equally strong observations.

I've read a lot of research on fMRIs and mental disorders. Something like this pops up every other day. Not a single one has really study the test of time ion terms of diagnostic utility.