We had to take into account nicotine use and alcohol use because they do impact the brain. We were able to control for a number of substances, a number of variables, in our analysis. We have seen that nicotine use does impact the brain, particularly in high doses.
We're just making the statement that you have to consider all drugs. They interact when they're used at the same time, in the same person. It all has to be taken into account, because it's not a benign drug either.