I was diagnosed with ADHD at the age of 2 years old after getting the chicken pox vaccination, all my life I was scared of people making fun of me because of being considered ESE which is another way of saying special needs. To correctly answer the question; no it does not effect ones intelligence but only makes it a bit harder to put full focus on the task at hand. If you are ADHD and would like some more information please contact me as I have had it many years.
It doesnt affect the intelligence itself.
What it does effect though is your ability to use your intelligence. If you cant concentrate on a task you might not be able to complete it, even though intelligence-wise you would be able to.