Does smoking weed make you dumber?

Tegan Taylor: Even a decade or so ago, cannabis was pretty much you could get it in Amsterdam legally and not very many other places in the world. Norman Swan: However, there's a second study which came out recently this year from very good centres, I mean, the University of Oxford, Yale University, looking at brain structure and function in cannabis use, doing quite a sophisticated association using something called Mendelian randomisation. So a lot of studies that are looking at brain function, and I'm not an expert in this area but I do know that a lot of studies that are done, they do very appropriate, sophisticated measurement of brain function and all of those kinds of things, but it's often once people have already started using, so it's difficult to know… Norman Swan: Before and after. Norman Swan: And two papers really with good news, because if you're a woman in childbearing years, you often don't know you're pregnant early on, and if you're using drugs like cannabis or alcohol, you just can't be sure and then you find out you're pregnant, you think, oh my God, what's going to happen to the child, but there's actually quite good news from two studies. Norman Swan: So it's not that we're going to encourage cannabis or any other drug use in early pregnancy, but there is cause for reassurance if you're one of those people who… Louisa Degenhardt: If you have.