ADD and a pre-teen...medication or hormones??

I have a boy almost 12 who is pre-puberty and trying to be very independant. He was diagnosed ADD 2 years ago and has been taking Adderall XR 10mg. since then. He loves to have the last word and of course is always right, hates housework, homework and discipline. His mouth runs alot! and gets him into trouble often. Since school is out for the summer, i have accidentally, on purpose?, forgot his medication on days that he has slept in....and his mood seems to be more laid back and not so angry on those days. Could this be a sign that the med. is causing the irritability? or is it just a coincidence of having a good day. Of course, this is something i will discuss with his doctor, but, I was just hoping maybe someone with knowledge or with ADD could give me some perspective. Hormones of a pre-teen or medication?? Thanks!