BTW, I don't think they have a total IQ score to look at. It looks like what they have is something they call the "Add Health Picture Vocabulary Test (AHPVT)," which the Add Health group describes as "... a computerized, abridged version of the Peabody Picture Vocabulary Test."
The Peabody Picture Vocabulary Test is something I'm familiar with because my son is deaf and had to take it all the time. I think it can be considered to be highly correlated with scores on the verbal portion of the IQ test. But overall IQ includes both verball and non verbal portions.
The other problem, if this is what's being used to make IQ determinations, is that the AHPVT is not the Peabody test. It's a "computerized, abridged version" of it. It could be that some work has been done to show that the AHPVT is correlated with tests of verbal IQ as the Peabody test is (
http://psychcorp.pearsonassessments.com ... d=PAa12010). But you'd have to look into that.
Right now I'm going on having gone to the "Ad Health" site (
http://www.cpc.unc.edu/projects/addhealth), gone to the "Study Design" link, clicked on each of the waves (I - IV), then done a "Find" on "test." The only psychometric test I found through that process is the AHPVT. If I get a response to my e mail to Add Health I'll let you know.