I really have no idea. What I do know is that if there is further drug testing and you test positive for something that you have not disclosed....that is not good. Also, if there is something that is preventing you from not doing your job correctly, and you have not disclosed it.... then you have possibly lost your chance from being protected by the American Disabilities Act.
So, if all is good with you at work....then I see no need to disclose what has happened in the past.
And, I might ask....why are you posting on the ADHD forum? I can help with ADHD questions. not so much with your kind of general question.
I hope this helps. And, if I can be of assistance with anything ADHD related - please ask.