The thing we call ADHD is just one phenotype amongst thousands. Every behaviour has a cause, and anyone out there who has been through a childhood with traumatic experiences and feelings of guilt and inadequacy need to understand that they don't need to be told that they have the currently-fashionable condition in order to forgive themselves.
This sounds flippant, but I don't mean it to be: What if I said that this happened because you had Mercury in Taurus? The point is here that nothing is your fault. Conversely, everything is; this mirrors the free-will vs predestination paradox.