Re Genetic Explanations of ADHD faulty?

I am using the book Taking Sides by Slife as a starting point. I have to present both sides of the issue. I will be faxing over the Issue by Jay Joseph and Faraone and Biederman. Jay Joseph takes the side that Genetic explanations are faulty. He says family studies and twin studies that have been done are faulty because they assume equal environments which cant be done because MZ have a different environment than DZ twins. He also says adoption studies are methodologically flawed because they dont use double blind studies.He believes psychosocial issues should be further explored. Faraone and Biederman say that they believe environment and genes both play a role but environment cant explain all of it. They also use molecular genetic studies and talk about how studies have shown dopamine is a canditate gene. I would like information on dopamine and how it works and how neurotransmitters in general work and what areas of the brain they affect (which goes back to why dopamine is a candiate gene). I would also like to explore some environmental issues talked about. Like smoking and drinking alcohol while pregnant, prematurity and marital discord have all been linked to ADHD. And any thing else you might be able to find. Basically I just need to talk about how the genetics of ADHD might be faulty and why the might not be faulty.