I'm also going to recommend not saying anything. Your child gains absolutely nothing by disclosing this information, but will close the door to certain MOS/ratings/jobs if they do. If it won't come up on some type of criminal record/report, and there are no scars or physical signs of it, they really have no way of finding out. Your child will sign a medical release form, but unless they call the specific Dr. that prescribed the drugs, or the pharmacy that issued them, they're not going to find anything. Some branches have a day early on in boot camp where someone comes in and tries to scare people into disclosing things that might not be on their medical record, don't say anything and they won't find out.
I was on 3-4 different ADD/ADHD meds as a kid, dislocated my shoulder, and had minor knee surgery. I didn't tell them anything, they didn't find anything.
ETA: Didn't realize I was bumping an old thread, sorry
Any news on this?