What was your experience with a young diagnosis? I feel nervous for my son.

My son is 10, soon to be 11 this month. He has had behaviors that I really think is ADHD and so does his pediatrician. He is starting to struggle daily now. I also am a BCBA so Im a bit familiar… We have an evaluation on Friday and I am anxious/nervous. Mostly because I think he will need to be on medication and I feel guilty. I know there is nothing wrong with medication and it could be great when needed. I am just afraid what it will do to him, how it will affect him now and long term. Im looking to see people who got diagnosed at a young age and how that process was/is. With medication and everything. My fear is that it would change the positive things about him as well, and if it will alter his brain chemistry in certain ways permanently since he is starting so young