You made a statement, you should prove it. You should not ask others to debunk a statement you made.
Regardless, here is the first study in Google I found.
*www.ncbi.nlm.nih.gov/pmc/articles/PMC4031582/
This study is not 100 percent conclusive, if you have a study that claims otherwise, please link.
I am not going to delude anyone into thinking ANY study like this can be conclusive. Not at all, there are too many variables involved. But when lawmakers use their pre-conceived notion and bring in arbitrary laws WITHOUT any study, that's a call for protests. IMO, any law that comes into effect because of some study, however biased it might be, it has to be in public domain. Lawmakers dont get to tell us, dude trust me.. this is for the best and pass in some judgement.