Nevuela I'm sorry to hear that happened too you. The little research I have done to this point states that roughly 20% of cases of ADHD are caused by external events. Things like ongoing chemo, physical trauma like abuse and so on.
My son has extraordinary circumstances and many side effects from the chemo treatment. He has ongoing physical therapy due to damage done to ligaments and his muscular system. Occupational therapy for the neurological damage that affects his writing ability. E.g. His 7 year old sister is more advanced in her penmanship then him by long shot and he is approaching 10.
He went through a battery of behavioral exams as did my wife, me, and his teacher to determine what is going on with him. He is also scheduled for a thorough psychological work up as he struggles with anxiety and depression. So his diagnosis was not determined flippantly.
My wife and I are in no way opposed to medication. However due to his recovering from a battery of medications we will be taking a break for a little while, and reexamine it on an ongoing basis. We are currently working up strategies to help him develop the executive functions he needs to be an independent socially adjusted responsible adult. We have also seen tremendous improvement over the last year since he has completed his chemo. As an example when he started regular school last year he was two years behind where he needed to be and was disruptive in class. Roid rage sucks. Part of his protocol was a heavy dose of steroids a week out of every month. Now within a single year he is caught up to his grade level and ahead in some areas, and does not have any behavioral issues at school.
Again thank you everyone for your insights as we will be considering and utilizing all your knowledge in one way or another to help us help him.