Ok, this is just what I'm finding right off hand without looking too hard... I will continue looking later this weekend to see if I can find the more detailed stuff I had read before.

But basically it's sounding like these things - especially attention disorders - are very multifaceted and have biological and environmental components. It's the whole issue of nature vs. nurture. Obviously both are very very important, but there are certain "nurture" things that can exacerbate or "turn on" certain "nature" aspects.

http://pediatrics.a...abstract/126/2/214 (pediatrics.aappublications.org)
http://archpedi.am...bstract/163/11/1037 (archpedi.ama-assn.org)
http://pediatrics....ent/short/120/3/532 (pediatrics.aappublications.org)
http://jad.sagepub...4709347205.abstract (jad.sagepub.com)
http://pediatrics.a...abstract/120/5/978 (pediatrics.aappublications.org)
http://repository....ontext=ircs_reports (repository.upenn.edu)
http://www.medical-...2900530-1/abstract (www.medical-hypotheses.com)