TLDR: I’ve been on Adderall over ten years and no known long term problems attributable to my meds. You should share your concerns with a/multiple doctor(s).
I’m not the parent but since no one answered: I was diagnosed in early childhood but only started meds around 21 years old (the first time I took Adderall was the first time I wrote an outline for a paper) and I’ve been on it nearly continuously for 13 years now, almost at the maximum dose. So far, no side effects at all of long-term use other than a learned behavior of building anxiety and stress every month around the time of getting my perception due to the war on drug style of regulation. I have only rarely had short term side effects when only taking extended release Adderall.
On your concern generally, I’m not a doctor but I’m not sure long-term effects should be a big concern without some known contraindication. To my recollection, none but my current doctor have given much discussion to long term effects of Adderall, if at all. My current doctor (who I believe had finished residency shortly before I started seeing him) was concerned about long term (heart) effects and I asked him for some links to info/studies. He sent me a webmd link to an article discussing a paper examining cardiac events in Canadian patients over 65 recently starting Adderall, which found no increased risk of cardiac events vs those not starting/taking Adderall. I don’t think there were conflicts of interest declared but it seemed like some authors had some association with the Shire pharmaceutical company. For context I’m mid 30’s, American, and have been taking Adderall as a long-term patient so I was confused about why he would send that but he didn’t expand on it when pressed. Research I did on my own only led me to studies showing that people with ADHD are twice as likely to of die in an accident as non-adhd counterparts, which I had never heard from any doctor and I believe is the leading cause of death in my age group.
As another note, my uncle was prescribed Concerta for an off-label use and quickly started having suicidal thoughts and stopped using it. Work with a physician who feels like a good match with you so you can be candid with them.