Again "Study shows" not actual proof, just a small study and its results. You can drag these "study's" from everywhere there's loads of them not there's none been done on a large enough scale to provide incontrovertible proof of its findings.
And for my own opinion I think tighter limits should be set on alcohol, tobacco or anything that effects your mental state outside of a legal prescription by a doctor, and they should be enforced especially when it involves driving or control of vehicles.