Interventional studies can be like the GAP at WDW and get you in sooner, but there's always the "risk" your kid will get the placebo and you'll be committing to a year of appointments and blood draws to be part of the control group. Or that he gets the "drug" and it turns out to make no difference or makes things worse. Or that it's really helpful, but that you can't get the medication once the study ends.
I wouldn't sign on unless I knew what the medication was. DH is a rote skeptic about such things having worked in the drug industry. Is it the vasopressin?
I've never done an interventional study with DS. I have a couple of friends who have been part of a trial cohort. None of them has had anything earth-shattering as a result; two participated in trials that were shut down mid-trial.
Good call, I'll plan on bringing it up with his psych next month. I got a call back immediately from UMN, they are going to start enrolling his age group in a few months. I'm not excited about the placebo possibility.