A plain ADD diagnose is just a starting ppoint to begin sorting other clinical issues out, meds and therapy.
Now days most of ADD cases are associated with COMORBILITIES,being ODD (Oppositional Defiant Disorder) and GAD (General Anxiety Disorder) the most relevant and the entry door for AOD (Alcohol and other drugs) use and abuse.
ODD appears usually in the early years 4-6, but it can continue showing different manifestations related to age and circumstances.
Many details to evaluate: only child? Has brothers/sisters? Does he have contact with his father? What are his interests, hobbies? How has he been disciplined? Etc.
Hope you find the correct clinical/medical path and action for the benefit of all. Rgds. MEH